Forever off.
If I towed, I might use a trans temp defuel as an alert.
The "factory" defuels are so arbitrary and easily eclipsed by what I consider perfectly safe tuning on some trucks.
My gig is that if I'm all the way off in it, I don't want anything pulling me out of it! LOL
On the 4th gen dodges, defuels are dangerous and typically cause more problems than they prevent.
I grew up on 12v's, so when I came over to electronic trucks, I stuck with the mantra of leaving it on constant kill