Auto log out
For security, the default setting is for the app to automatically log you out when not in use. If you are not using a shared device, you can turn this feature off by going to Account > Settings. The onus is then on the user to manually log out as required.
App: You will be logged out when the app is not active. E.g. you have restarted your phone or closed the app by swiping it away.
Browser: You will be logged out when the window is closed.