You literally only have seconds to get yourself out of a hanging position even in a full body harness. And yes, every year they find people dead dangling from their harness, belt or other wise. Best way to save your butt is to not only wear a full body harness, but to also have a plan that will get you out the hanging position and back on your stand or safely climbing back down to terra firma.
I agree, just hanging there waiting for your hunting buddies to come around and help you out isn't proper risk management. I should clarify: what I meant was that hanging from a harness as opposed to a belt gives a person more mobility to perhaps recover i.e. grabbing something nearby even if it is the base of the tree itself. If there are limbs or the stand is still intact and adhered to the tree you can grab that and recover.
With the belt you may be hanging upside down and yes, constricting your chest which would impair breathing. That would be very difficultto recover from.