My current stable is 5 basses, and that's the most I've ever owned at one time in ~35 years of playing. I'd have to say that the Alien Audio Lunar 5 gets the most use by far, but then again it's arguably the most versatile (Nordy Dual Coil and Big Split, 3-band, passive tone, modern/vintage switch, onboard overdrive).
I also have a fretless 'Ray 4, so it's hard for me to say that I could get by with just
one bass bc I see the fretless as an entirely different type of tool. I have used it many times to record with, but I only play it live when we do a gig comprised of original material. You'd never catch me showing up to any gig with more than the two basses though.
Having a handful of basses also affords me luxury of keeping one at our band practice space -- I just show up, plug in and go.
In a nutshell, I could do the one bass thing but I'm fortunate I don't
have to.