There are a couple of different "idle limits". One is the time to screen lock or sleep on the iPad -- this is indeendent of FMP. Another is the idle time in the privilege set in the FMP database itself.
My guess is that the device sleep/lock is the one you need to look at.
There is an extended privilege that allows auto-login from an iOS device, this will save having to re-authenticate each time the device is unlocked.
I am aware of the sleep / lock on the iPAD and it will be set to "never".
I will research futher the privilege set and extended privilege. Since the dvice will not be going asleep I think I'll concentrate on the privilege set in the FMP database.