My experience has been that I have enough basses if I have one instrument in my collection that I want to play exclusively. If you own one bass that makes all the other ones redundant, you have enough. Sometimes I get tired of the "number one" and switch to another instrument I already own, or sometimes I get rid of some gear and buy something else. I guess my goal is to have a collection made of only current or past "number ones". If I have a bass I never want to play, I will eventually sell it.