I'd have to agree with dyza that the polyps have something to do with the sense of smell. I'm not sure if repeated polyp removal would have anything to do with it, though.
I was without the sense of smell, taste, and even being able to breath through my nose for several years before I had my polyp surgeries done. I had to go in two times, the second time was the biggest, and was done about six months after the first.
After everything healed, I was able to taste, and smell things right away. It was amazing what familiar tastes I went so long without.
The surgeries were at least 25 years ago, and I had no problems since then. I would get occasional sinus congestion, and short-term loss of senses for taste and smell, but they would eventually come back. Even when I had a few allergy attacts, or was suffering from seasonal allergeis, my senses would eventually return.
I found recently, that gargling with some sort of Japanese brand Iodide diluted in warm water, and running it through my nose really seems to do a job on keeping the senses intact.
I'm surprised how many other CF'rs don't have a sense of smell, do you all also lack the sense of taste, too? My senses are keen enough to even distinguish when Fall, or Spring is in season, and even be able to tell when a bad rainfall is coming, soon! I can catch the smell of a cigarette almost 100 meters away, and will avoid that asap!
I do hope there is a method to bring back the sense of smell, I'm sure it does have an effect on the sense of taste, and when those senses are not working, you're missing a lot!