diff --git a/src/notifications/schedulers/ETANotificationScheduler.ts b/src/notifications/schedulers/ETANotificationScheduler.ts
index 4e0227a..234b310 100644
--- a/src/notifications/schedulers/ETANotificationScheduler.ts
+++ b/src/notifications/schedulers/ETANotificationScheduler.ts
@@ -3,27 +3,26 @@ import { TupleKey } from "../../types/TupleKey";
 import { IEta } from "../../entities/entities";
 import { AppleNotificationSender, NotificationAlertArguments } from "../senders/AppleNotificationSender";
 
-export interface ScheduledNotificationData {
+export interface NotificationLookupArguments {
   deviceId: string;
   shuttleId: string;
   stopId: string;
+}
 
+export interface NotificationSchedulingArguments extends NotificationLookupArguments {
   /**
    * Value which specifies the ETA of the shuttle for when
    * the notification should fire.
    * For example, a secondsThreshold of 180 would mean that the notification
    * fires when the ETA drops below 3 minutes.
-   *
-   * Optional to retain backwards compatibility with devices on the
-   * older API version.
    */
-  secondsThreshold?: number;
+  secondsThreshold: number;
 }
 
 type DeviceIdSecondsThresholdAssociation = { [key: string]: number };
 
 export class ETANotificationScheduler {
-  public readonly defaultSecondsThresholdForNotificationToFire = 180;
+  public static readonly defaultSecondsThresholdForNotificationToFire = 180;
 
   constructor(private repository: GetterRepository,
               private appleNotificationSender = new AppleNotificationSender()
@@ -44,7 +43,7 @@ export class ETANotificationScheduler {
    */
   private deviceIdsToDeliverTo: { [key: string]: DeviceIdSecondsThresholdAssociation } = {}
 
-  private async sendEtaNotificationImmediately(notificationData: ScheduledNotificationData): Promise<boolean> {
+  private async sendEtaNotificationImmediately(notificationData: NotificationSchedulingArguments): Promise<boolean> {
     const { deviceId, shuttleId, stopId } = notificationData;
 
     const shuttle = await this.repository.getShuttleById(shuttleId);
@@ -82,7 +81,14 @@ export class ETANotificationScheduler {
 
     const deviceIdsToRemove = new Set<string>();
     for (let deviceId of Object.keys(this.deviceIdsToDeliverTo[tupleKey])) {
-      const deliveredSuccessfully = await this.sendEtaNotificationImmediatelyIfSecondsRemainingBelowThreshold(deviceId, eta);
+      const scheduledNotificationData: NotificationSchedulingArguments = {
+        deviceId,
+        secondsThreshold: this.deviceIdsToDeliverTo[tupleKey][deviceId],
+        shuttleId: eta.shuttleId,
+        stopId: eta.stopId,
+      }
+
+      const deliveredSuccessfully = await this.sendEtaNotificationImmediatelyIfSecondsRemainingBelowThreshold(scheduledNotificationData, eta.secondsRemaining);
       if (deliveredSuccessfully) {
         deviceIdsToRemove.add(deviceId);
       }
@@ -93,16 +99,12 @@ export class ETANotificationScheduler {
     });
   }
 
-  private async sendEtaNotificationImmediatelyIfSecondsRemainingBelowThreshold(deviceId: string, eta: IEta) {
-    if (eta.secondsRemaining > this.defaultSecondsThresholdForNotificationToFire) {
+  private async sendEtaNotificationImmediatelyIfSecondsRemainingBelowThreshold(notificationObject: NotificationSchedulingArguments, etaSecondsRemaining: number) {
+    if (etaSecondsRemaining > notificationObject.secondsThreshold) {
       return false;
     }
 
-    return await this.sendEtaNotificationImmediately({
-      deviceId,
-      shuttleId: eta.shuttleId,
-      stopId: eta.stopId,
-    });
+    return await this.sendEtaNotificationImmediately(notificationObject);
   }
 
   /**
@@ -113,17 +115,13 @@ export class ETANotificationScheduler {
    * @param secondsThreshold Value which specifies the ETA of the shuttle for when
    * the notification should fire.
    */
-  public async scheduleNotification({ deviceId, shuttleId, stopId, secondsThreshold }: ScheduledNotificationData) {
+  public async scheduleNotification({ deviceId, shuttleId, stopId, secondsThreshold }: NotificationSchedulingArguments) {
     const tuple = new TupleKey(shuttleId, stopId);
     if (this.deviceIdsToDeliverTo[tuple.toString()] === undefined) {
       this.deviceIdsToDeliverTo[tuple.toString()] = {};
     }
 
-    if (secondsThreshold !== undefined) {
-      this.deviceIdsToDeliverTo[tuple.toString()][deviceId] = secondsThreshold;
-    } else {
-      this.deviceIdsToDeliverTo[tuple.toString()][deviceId] = this.defaultSecondsThresholdForNotificationToFire;
-    }
+    this.deviceIdsToDeliverTo[tuple.toString()][deviceId] = secondsThreshold;
 
     this.repository.unsubscribeFromEtaUpdates(this.etaSubscriberCallback);
     this.repository.subscribeToEtaUpdates(this.etaSubscriberCallback);
@@ -135,7 +133,7 @@ export class ETANotificationScheduler {
    * @param shuttleId Shuttle ID of the ETA object.
    * @param stopId Stop ID of the ETA object.
    */
-  public async cancelNotificationIfExists({ deviceId, shuttleId, stopId }: ScheduledNotificationData) {
+  public async cancelNotificationIfExists({ deviceId, shuttleId, stopId }: NotificationLookupArguments) {
     const tupleKey = new TupleKey(shuttleId, stopId);
     if (
       this.deviceIdsToDeliverTo[tupleKey.toString()] === undefined
@@ -153,7 +151,7 @@ export class ETANotificationScheduler {
    * @param shuttleId
    * @param stopId
    */
-  public isNotificationScheduled({ deviceId, shuttleId, stopId }: ScheduledNotificationData): boolean {
+  public isNotificationScheduled({ deviceId, shuttleId, stopId }: NotificationLookupArguments): boolean {
     const tuple = new TupleKey(shuttleId, stopId);
     if (this.deviceIdsToDeliverTo[tuple.toString()] === undefined) {
       return false;
@@ -165,19 +163,21 @@ export class ETANotificationScheduler {
    * Return all scheduled notification for the given device ID.
    * @param deviceId
    */
-  public async getAllScheduledNotificationsForDevice(deviceId: string): Promise<ScheduledNotificationData[]> {
-    const scheduledNotifications: ScheduledNotificationData[] = [];
+  public async getAllScheduledNotificationsForDevice(deviceId: string): Promise<NotificationLookupArguments[]> {
+    const scheduledNotifications: NotificationSchedulingArguments[] = [];
 
     for (const key of Object.keys(this.deviceIdsToDeliverTo)) {
       if (deviceId in this.deviceIdsToDeliverTo[key]) {
         const tupleKey = TupleKey.fromExistingStringKey(key);
         const shuttleId = tupleKey.tuple[0]
         const stopId = tupleKey.tuple[1];
+        const secondsThreshold = this.deviceIdsToDeliverTo[key][deviceId];
 
         scheduledNotifications.push({
           shuttleId,
           stopId,
           deviceId,
+          secondsThreshold,
         });
       }
     }
diff --git a/src/resolvers/MutationResolvers.ts b/src/resolvers/MutationResolvers.ts
index c1a4ce3..93ae763 100644
--- a/src/resolvers/MutationResolvers.ts
+++ b/src/resolvers/MutationResolvers.ts
@@ -1,5 +1,9 @@
 import { NotificationInput, NotificationResponse, Resolvers } from "../generated/graphql";
 import { ServerContext } from "../ServerContext";
+import {
+  ETANotificationScheduler,
+  NotificationSchedulingArguments
+} from "../notifications/schedulers/ETANotificationScheduler";
 
 export const MutationResolvers: Resolvers<ServerContext> = {
   Mutation: {
@@ -19,7 +23,12 @@ export const MutationResolvers: Resolvers<ServerContext> = {
         }
       }
 
-      await context.notificationService.scheduleNotification(args.input);
+      const notificationData: NotificationSchedulingArguments = {
+        ...args.input,
+        secondsThreshold: ETANotificationScheduler.defaultSecondsThresholdForNotificationToFire,
+      }
+
+      await context.notificationService.scheduleNotification(notificationData);
 
       const response: NotificationResponse = {
         message: "Notification scheduled",
diff --git a/test/resolvers/QueryResolverTests.test.ts b/test/resolvers/QueryResolverTests.test.ts
index 8b0b60e..c35be13 100644
--- a/test/resolvers/QueryResolverTests.test.ts
+++ b/test/resolvers/QueryResolverTests.test.ts
@@ -2,7 +2,7 @@ import { describe, expect, it } from "@jest/globals";
 import { generateMockSystems } from "../testHelpers/mockDataGenerators";
 import { setupTestServerContext, setupTestServerHolder } from "../testHelpers/apolloTestServerHelpers";
 import assert = require("node:assert");
-import { ScheduledNotificationData } from "../../src/notifications/schedulers/ETANotificationScheduler";
+import { NotificationSchedulingArguments } from "../../src/notifications/schedulers/ETANotificationScheduler";
 import { addMockShuttleToRepository, addMockStopToRepository } from "../testHelpers/repositorySetupHelpers";
 
 // See Apollo documentation for integration test guide
@@ -108,7 +108,7 @@ describe("QueryResolvers", () => {
       const shuttle = await addMockShuttleToRepository(context.repository, "1");
       const stop = await addMockStopToRepository(context.repository, "1")
 
-      const notification: ScheduledNotificationData = {
+      const notification: NotificationSchedulingArguments = {
         shuttleId: shuttle.id,
         stopId: stop.id,
         deviceId: "1",