I wrestle with this. Last time I went to count lenses, it was something over 50. The problem is I bought them for different reasons, and they still fit that. For example, I have two Takumar 3.5/135. One is SMC, and one is not. How else could I see what the SMC coatings really would do? Now I know when I buy vintage lenses, get the SMC variant. Should I sell the other one? Perhaps, but then the collection would be missing a piece and is it really worth the time and effort to maybe clear $15-20 bucks after eBay charges etc. when I could just keep it? I have two 15 Limiteds - SMC and HD. The HD does better on contrast and pop on a nice sunny day, but the starbursts on the SMC are fantastic! How could I sell either? So, it's easy for non-believers to cast dispersion upon all these flavors and piles of glass, but for those who have seen the light, it makes perfect sense. Lots of fun and enjoyment in seeking out different lenses and seeing what they and you can do. If they cease to deliver pleasure and represent opportunity cost, cut them loose, otherwise, as long as you get enjoyment out of them and still have food on the table, kick back and smile. Life's too short to get too bent on some of this stuff.