The soft client (app) utilizes the PennKey Single Sign-On (SSO) system (also known as Penn WebLogin). As such, it is affected by the system's University-wide policy of automatically logging out after 30 days if it's not renewed. The soft client (app) will display a banner message with a # of days left before it will sign you out. From that banner message you can renew the login for another 30 days.
At this time, there's no plan to change the policy but if there is this document will be updated to reflect that.
This does not affect the physical handset at all.
If you require further assistance after going through this knowledge article, please submit a ticket at support.collegehouses.upenn.edu.