Q: How often should a tracker sync to the Fitbit App on a user's phone with and without All Day Sync enabled?
With All Day Sync disabled in the mobile apps, the devices will attempt to sync only when someone opens/resumes the Fitbit app. It will sync every few minutes while Fitbit is the foreground app.
With All Day Sync enabled in the mobile apps, the devices will attempt to sync every 15–20 minutes. However, this is subject to the mobile phone’s scheduling and connectivity. If someone’s device is memory constrained, the Fitbit app won’t be allowed to run in the background. If someone is using an iOS or Windows device in low power/battery saver mode, the Fitbit app won’t be allowed to run in the background. If someone disables Bluetooth, the background syncing will stop.