I think a part of why I have so many is the insulting offer they make when you suggest you might want to trade in your lens on a new one.

I end up just buying the new lens and keeping the old one instead of letting it go at 10% of what I paid for it.

A better question might have been - how many lenses do you regularly use. In that case the answer would have be 3.

- Nikkor 17-35mm f/2.8
- Tamron 28-35mm f/2.8
- Nikkor 80-200mm f/2.8

25 for Nikon
5 for micro 4/3
8 for 4x5