On any normal day, I would choose one or two lenses to go with a body I choose to use. The lens choice is usually the one I happen to like at the moment. I could use a particular lens for a week, but usually not longer than that. Because of the number of lenses I have, some of my old favourites have not been in use, or used very seldemly for years. The Carl Zeiss Jena Pancolar 80mm f1.8, and the Carl Zeiss Distagon 35mm f2.8 are two examples. Also, the Canon EF 35mm f1.4 is also one of my favourites, but not being used often. When I first acquired the EF 200mm f1.8L, I used to carry it and the 1Ds for days each time I went out until I couldn't take the weight any more. So, focal length doesn't play a role in being my favourite lens.
To conclude, I guess I just like variety, and always looking for the next favourite lens.
Click on the image to see a larger version:
Heavenly Temple -- Canon 1D & Carl Zeiss Jena Pancolar 80mm f1.8
Fall Leaf -- Canon 20D & Carl Zeiss Makro S-Planar 60mm f2.8
Romance on the street -- Canon 1D Mark II & Carl Zeiss Distagon 28mm f2.8