As I was composing my response in my brain (and thinking about the 'why' behind more basses that I desire) I realized that examining how we justify more basses when we probably have enough might be an interesting topic. Disclaimer: I'm not in any way insinuating that acquiring more basses, regardless of how many you already have, is morally wrong as there is no divinely inspired number we are limited to AFAIK.
That said, I have five, and only because I recently obtained two of them. I had a five, a six, and a seven, all of which I was happy with. I wanted another six, but decided to perform upgrades to mine to get what I wanted out of it. And another seven string was in order, so I could have both B-F and F#-C options.
Then a coworker gave me an el cheapo four string that needed repair. It has been revived and I plan on using it as a drop-D bass in the band I'm in. While my five string was perfect, I bought a BC Rich fiver from a friend of a friend (guess that makes them an acquaintance) and it too shall see action in my band.
Now that I have five I really don't want any more (yeah, I'm fooling myself there - still want another 7). I'd buy another sixer if I had the $$ and came across the right deal, but nothing is pressing me to do so. A Conklin Bill Dicken's sig model is next on the GAS list.
I live in a townhome so space is somewhat limited. I'm also more pragmatic than in the past, and would rather not keep stuff that just collects dust. If I can't use it, I usually wind up selling it.
Thanks for reading, it makes me feel like you care.

Raz