thank goodness my puppies have always managed all night fairly early on. Candy has had two accidents since I got her at 10 weeks old. Both times I had left her half an hour longer than normal. She has happily gone from 11pm to 7am the whole time though. I have never got up to a pup in the night and they have normally been totally clean by 12 weeks. I dont think you can put a formula on it.