I would assume that everyone is slightly different time-wise; my circulation sucks and I find my appendages falling asleep quicker than most. That being said you need to be aware of your own limits and those of your partner if you're going to have any kind of serious playtime. Try a dry run if you can, I know it sounds a little corny, but at least then you'll have some general idea. But of course, open communication is always the key to safety in play; if your hands start to get cold, numb or tingle you need to change things up and get the blood flowing again. But like I said, I think it's different for everyone.