In the documentation (https://www.opendrive.com/wp-content/uploads/guides/OpenDrive_API_guide.pdf) I found the duration of the session only in the case of login via oauth2 (chapter 15); in this case the duration is 24 hours. From what I have seen from rclone behavior the session expires after about a week and a half.
One possible solution is to check if the session is valid with the /session/exists.json call (section 8.2) before performing the operations.