did a quick search and there is a thread in the 5th gen forum about keeping the ACC on indefinitely.
Is there any way to make accessory stay on longer?
Folks are saying if you kill the rig in neutral then push the button without foot on brake it will keep the acc on indefinitely.
So this maybe my solution. got my buddy testing this for me now.
Start truck put on P-Brake - put in neutral - kill truck - hit push to start with out foot on brake. Put back in park. set timer and see what happens in 30 mins.