I have a TON of basses and I've decided to get down to a core 12 or so. I called my buddy Evan, one of the owners of Bass Northwest here in Seattle and I asked, "with so many outstanding basses constantly coming through your door, how do you decide which ones you want to keep in your personal collection and which ones go on the sales floor?".
I was told that pretty wood and paint, wiz bang electronics, etc. will ALWAYS present themselves, however If the tone and feel you are after aren't there, it goes on the sales hook. It really comes down to being business-like and honest with ourselves on these issues. This line of thinking makes my decisions VERY easy now. Yes, I have a couple of basses that have sentimental and historical value that I plan on hanging on to, but you get the drift.
Hope this helps.
KT