I played the "buy it again after selling it" game with Leicas and Leica lenses, sometimes even failing to learn after one cycle. Eventually I trimmed that side of things down to an M2 and three Leica lenses (plus one CV). The issue turns out to be that I really do prefer an SLR to a rangefinder. The M2 stays around simply because those Leica lenses are the best, technically, that I have. I don't want to think about how much money I sank into all that; it makes me feel as I imagine someone does at Gamblers Anonymous. The M2 and lenses will go in the next year or two when the alternative is to start dipping into my retirement savings, or as soon as the leukemia relapses, whichever comes first
Since then my re-purchases have been more rational: replacing an old broken camera, or buying a spare in anticipation of the breakdown of one I don't want to be without. That's an indicator of something, isn't it? The cameras you buy as spares as you don't want to live without them. Oddly, the spares have not been my most used cameras, except for the F6, and I bought a second F6 simply because I use it a lot and wanted the ability to have B&W and colour. I have bought a spare Pentax ME Super, two spare ($25 each, why not?) Pentax SF1n's, a spare Olympus OM-2n, and a Pentax 645nII. I suppose I would have a spare Rolleiflex, but to have a decent inbuilt meter I'd be looking for a GX and can't justify the cost.
This makes me think a little on which cameras I do use the most. I think it would look something like this:
35mm
Nikon F6
Pentax SF1/SFX
Olympus OM-2n
Leica M2
Various manual Pentaces
Olympus Pen F/FT
(sold two FM3a bodies and all manual Nikon lenses)
MF
Rolleiflex 2.8GX
Pentax 645n
Hasselblad 500
(sold a Bessa III, Fuji GA645, Fuji 690III)
LF
Chamonix 10x8
Chamonix 4x5
Crown Graphics
If I had to, and perhaps one day I shall, I could be happy with an F6, the Rolleiflex and the Chamonix 10x8. My situation is perhaps a bit different to most, in that I have a very large frozen stock of film, a bunch of cameras, and insufficient time to consume it all. Other things being equal, it's a nice problem to have!