DS is 2 1/2 and we've been doing BD's (Bronchial Drainage) or manual CPT 3 times a day since DS pretty much since he was born along with albuterol and atrovent. We also do tobi twice a day and pulmozyme once a day (just started that in September).
DS's CF doctor stressed how lung care was oh so very important even if the lungs aren't having problems yet. I remember him saying that other doctors will tell you nutrition is more important, but one can always add calories, you can't regain any lung tissue that is lost. He said the more beatings the better -- at bare minimum twice a day, 4 times would be ideal, but we as parents need to have a life, as does our child.
Our local doctors are more reactive than proactive and questioned our doing CPT and nebs at all. In any event, we figure we'll do whatever we can to keep ds's lungs healthy.
On a side note, I was horrified when DS was first diagnosed and read a post on another site from a parent who injured her arm and just skipped her child's CPT all together 'cuz she had a cast. Heck, I can do one handed CPT when DH is at meetings. Takes a little longer, but it can be done.
Liza