I'll do an experiment to help you guys figure this out. Me and a friend will pack a bowl, only he'll smoke it and we'll use a cardboard tube to shotgun it into my mouth and I will only smoke what he shotguns to me. If I get high, that means that there is still THC left and it's worth it to hold it in. If not, I'll just smoke a bowl and get high anyway! I'll be back within 24 hours with the results . . .