This may make things worse to know, but my son is 14 3/4 and still wets the bed. We have tried everything and nothing works. We were told that this is normal until they are 18 and then a small percentage will always wet the bed. It is much worse when he is on IV's verses not on IV's, but even off IV"s he may get 1 or 2 dry nights if he is lucky.
The one thing that has kind of helpd, or at least lessened the amount some is eliminating caffiene.
I didn't read all the posts but from what we were told, this is a common issue with CF.