CF affects every person differently, even identical twins. One person's PFTs may drop and then rise back up, another may remain stable for many years, another may slowly drop over time...It's just so hard to predict. If Patricio's PFTs are in the low 30s because he's having an exacerbation, it might be possible for them to return to his baseline after hospitalization and/or IV antibiotics. Exercise and airway clearance are also very important.
I'm 29 and my PFTs have been in the low 30s for several years now. They drop a little when I get sick and come back up a little when I get better. But as hard as I've tried, I can't seem to get them over 40%. As I said before though, that is just my experience. And it certainly doesn't discourage me from trying to get and keep them up. I think mental attitude has a LOT to do with physical outcome, personally.