My DD isn't a very big wetter so I usually change every 3-4 hours, after her bottle usually. Thats what works for us, she never leaks and she has never had a nappy rash.

But I agree with Leasha - get to know your nappy - My DD has one brand of nappy that she can only wear for 2-3 hours absolute max, and sometimes it leaks then, so yeah, really does depend on the nappy.

Good Luck in finding your happy nappy time