Every 2-3 hours. Mostly the door is open for Boris most of the time, and I don't really watch him out anymore, my guess is that he pees probably 6-8 times a day. For Tips, every 2-3 hours is fine, he just holds (at 2 months, I'm so proud). We let them out last thing before bed at night (between 10 and 2am basically) and they hold until 8-9am without a problem... even Tips.