Hi Shawn;
I would implement a "Heartbeat" feature like I've implemented in my STD Framework. Each App can have its own HB timer & DML command. Thus not only does this solve the PS session timeout but any DB timeouts as well.
Personally, I don't like playing with these timeouts in the web server, PS server or DB server as the defaults are typically designed to capture other processes (apps) that are not behaving up to default standards.
Also, don't forget to code the App's IDLE event as well to shutdown the app after no user activity. This not only chews up a PS session but that also chews up your PS license's active count. So for example you have a 150 license. You normally run 120-140 concurrent users in your PS apps but, now 25 users have their apps minimized & still running. This means your using your 150 license count & only 125 new app users can log into your system. The other 15 users at peak times will not be allowed to start the App.
Food for thought. ;-)
Regards .... Chris