Yes, you can log in to three different devices concurrently. If you are already logged in to three devices including mobile devices and desktop app sessions and try to login to a fourth, you will receive a message informing you that you first need to log out from one of the other devices.
To avoid accidentally maintaining active logins on redundant devices, a script is run every day to automatically log out accounts that have been inactive for over 30 days.
If you need help logging out from your sessions, please Contact Us.