Not to sound overly like a diplomat here, but I think we've probably hit on the #1 difference between CF care today and CF care back in the 70s/early 80s, and that is that it wasn't really standardized yet. Considering how much variation there can still be among clinics, even with the CFF's attempts to standardize guidelines, it doesn't exactly surprise me that parents at that point were given conflicting info re: life expectancy or that treatments/care regimens varied sharply from center to center. In other words (here's the diplomatic part), I think it's quite possible that we're all right here.
I was diagnosed in 1981 at 6 weeks old by sweat test. At that point I think the life expectancy was probably around 18 years old. But the exact words of the doctor to my parents were "take her home and love her as long as you have her." Not exactly inspirational. My parents were then set up at a CFF clinic, where they got me on manual physio and started me on enzymes and nebulized tobra and mucomyst pretty early on (I remember doing it at like 3 years old). I never had any surgeries or bronchs though, and I never slept in a tent.
One thing is for sure, Suzie - your mom is right that you're son is lucky to be a CFer now rather than 30 years ago. I'm amazed at the new drugs we have on the market, or close to the market, and this generation gets all the benefits of starting those EARLY.