It depends on the lens. I don't use filters unless I have a photographic problem that the filter will solve and then it is only a polarizing filter or Graduated ND filter. I do have some of the Nikon Clear lenses for when I am shooting in blowing sand, otherwise, no filters here. Most of the time to clean my lens, I just blow my breath on them and use a microfiber cloth to clean off the fog. When that doesn't work, I use Formula MC lens cleaner. That is about once per year. Anytime I pull the camera or lens out of the camera case, I use a squeeze bulb to blow any dust off it and twice a year, I vacuum the inside of my camera cases (I have about 5 or 6 cases. There are many ways of doing this and this is just MY way of doing it. What I don't like about a UV filter is that it does alter the color balance where as a clear filter doesn't.

I clean the wide angle lenses more than I do the telephotos becasue the dust doesn't show in the photo from a telephoto unless it is REALLY BAD, but I don't let them get that way in the first place.