Originally posted by richardwong Greg - I can see what you mean, but which ones would you keep then and how many?
I think a general rule applies: keep the one's you use on at least a semi-regular basis. I have lenses, for example, that I never use and never want to use (DA 18-55 I, M 28/2.8, M 50/2, Vivitar 80-200/4.5). They're hardly worth the trouble of selling, which is another issue.
I'll keep a lens if (1) I like what it produces (particularly in terms aesthetic qualities, not just sharpness or other numerical specs); and (2) It fits my shooting style. I don't own any fast wide angle or normal FOV lenses because I don't need fast aperture at those focal lengths. I don't own the DA* 55 or the FA 77 because I'm not a portrait shooter.
One of the reasons I've wound up with so many lenses is that I prefer primes but sometimes require the focal range versatility of a zoom. So I have landscape prime kit (DA 15, M 20/4, K 28/3.5, K 35/3.5) and a landscape zoom kit (FA 20-35, FA 24-90). I have two primes for critters (DFA 100, DA* 300) and a zoom for critters (Tamron 70-200). Then there are the specialty lenses as well (K 50/1.2, F 85/2.8 Soft). All these lenses get some use. Some, like the DA* 300 and FA 20-35, get a lot of use. Some, like the DA 15, the K 35/3.5, the K 50/1.2, and the DFA 100, I wish I could use more often, as they are stellar lenses but aren't needed that often. That's the chief problem with having too many lenses, particularly too many superb lenses: there's glass that's bound to get neglected, unjustly.