For me, I only pee in my diapers. Kind of depends on my mood I guess. Sometimes I'd stay in it through a second wetting, sometimes I'll change ten minutes later. I guess the longest I've ever stayed in a completely soaked diaper is two hours or so.
I recently wet right before I went to sleep and I feel like that was a bad idea. After I woke up the next morning, I basically had diaper rash. Luckily it didn't last very long and I was able to walk again with comfort after a couple hours.
So probably, not more than 8 hours, lol. I'm still rather new to actually using diapers for their intended purpose at all so I'm kind of finding things out the hard way.