The time the possum will play dead varies but when they come up against a threat and they get that involuntary response the possum will then play dead for a period of between 40 minutes to as long as 4 hours.
When a possum faces something that is a threat they naturally get stressed out as a result of the threat and that natural threat causes the possum to go into a comatose state that is involuntary.
So the possum then goes into a playing dead state and then eventually the possum will come out of that comatose state and then come back to life.
Well it didn't really die although it will seem like it because that's what they are doing playing dead.
If the possum is still alive they should come back and wake back up after at least 4 hours and if not the possum may actually be dead.