I got some info from the RCH Melbourne website which says that about 1 in 3 wet the bed at age 4, dropping to about 1 in 10 by age 6, then 1 in 20 by age 10. So it's pretty common, and it's often not as simple as getting them to restrict fluid intake as the day goes on - some kids have smaller bladders, some are super heavy sleepers, some just don't produce enough of the hormone overnight that tells them they need to go to the toilet. I think it's a good article, it's made me feel comfortable about our situation, and is good because now DH is on board a bit more too , Might be worth a bit of a google.