I lived in wildeness for some time, and in my country it not rare activity, usually people do it for 3-15 days. And by it I mean not with car and e.t.c but with only things you could take with you by foot.
So for the polle -
Depends from to main factors:
1. Wildeness (climate, weather, dangers, and what is even more important if there are source of drinkable water)
2. Equipment.
Cause in European wildeness you even don't really need equipment, and in tropical forest during rain season not everyone even with good equipment would survive.
So I voted for first, but in some cases i wouldnt hold even for 6-10 hours.