Probably every 2-3 hrs during the day plus poos. Sometimes will be a bit longer if we're out or busy in the afternoon or she has a long sleep. We use mostly fitteds (bamboozles, LL, and some pretties) with PUL wraps during the day and rarely have any problems with leaking. I choose the nappy depending on how long I expect her to be in it and if I think she might poo soon
At night we use fitteds and wool and these go 8-12 hrs.