Remy is 15 months, 5.5 lbs
Overnight he can go 8-9 hours. He goes out the last time between 9:30 and 10:30, depending on my schedule and he is up ready to go like clock work at 6:30. He has actually been like this since he was 6 mos. Only difference is up until 1 year he used a pee pad first thing in the AM, now we go outside.
During the day, he waited 9 hours once. Interestingly, it was his own choice. We went to the U2 concert in DC - I left him at my office around 5pm. I knew it would be a long night so I gave my girlfriend (who Remy knows) my keys and she stopped by to take him out around 10. However, she brought her boyfriend with her and he did not know him.... Remy would not let them come near him. She finally had her boyfriend leave and got him outside, but he would not go. By the time we got back at 2am he reeeeally had to go, but did not have an accident

He got special treats for that!!!
Usually the longest I usually make him wait is 6 hours. He typically is out every 4 or so and if I lose track of time he lets me know