Some app settings are stored by user sessions and will revert to the default options when you log out of the app. This will include items such as voice feedback, units of measurement, coaching, bluetooth/device connections, live tracking, and more. In order to keep these settings in place each time you utilize the app, you must remain logged in.
Remaining logged into the app will not result in a battery drain unless there is a workout actively recording. Force quitting the app will allow you to remain logged in while ensuring it is not actively recording or using battery life.