I have five (though I have a sixth that I'm purposely not using because I agreed to sell it to fund my most recent purchase) that I'm quite happy with and have agreed to limit my collection to that number. But, I'm sometimes weak and will drool over a bass I see that's up for sale. So then I have to consider the likelihood that it could unseat one of my five before I buy any more and I usually pass because my current collection is more than good enough for my needs. As I've bought and sold basses, the likelihood of a new bass replacing one of these five has just gotten lower and lower over time.
Still, if I see one for sale that has a good chance of unseating one of my current basses, I'm willing to consider it.