It is an odd thing. I suppose we are only responding to urges which everyone has but we are expressing it in bass-dom.
In the past 2 years I have gravitated towards solid colour basses rather than natural wood ones which were my thing. The problem is that I have more than one bass which essentially do the same thing as soon as the Guitarmageddon kicks in.
A case in point is my MM5/G&L L1000/5 conundrum. As soon as I crank the bass on the MM (and why would I not?) or hit the afterburner switch on the G&L (and why would I not?) then they are much of a muchness. I know that there are all sorts of differences, but to own both "for that special moment" is difficult to justify. But I like them both.
The other side of the coin is that given that I buy carefully then I know I can get my money out of them easily so it could be a lot worse.
I would happily flog 3 or 4 if I could find one bass to rule them all, but every time I have bought that one bass, they have never hit the spot.