Everytime I have to move it - I am considering keeping just a M2 and a 35!! What happens is that I accumulate stuff and i am not good at selling any of it. My M2's,M6's and MP's as well as assorted M4P's and M4-2's are kept for checking Rapidwinders on ( as are my Leica screw mounts).
Some of the stuff are gifts from friends and thus cannot be sold, some of it dates back over the last 25-30 years and is still being used. Some of it is just "there" - no rhyme and reason.
I am not a collector - I only would keep a "collectible" if it has some practical use for me. There is also that fascination with mechanical toys - fiddling with shutters and controls, occasionally taking something apart and re-assemble it.
This is not the biggest "stash" I have had. When I used to work as a photographer, I had triple and quadruple systems, 35mm, 120 film, 4x5 and 8x10 - everything duplicated and matching coverage for several lenses. That stuff I unloaded in the early 80's and went back to 35 as my primary system
It is not a retirement portfolio - the value of the stuff fluctuates and I never expect to make my money back - but it all gets used one way or another and occasionally I trade an item for something else.
In the long run it is probably cheaper than golf - and I know that it is cheaper than trying to keep a vintage car on the road!!
I also like taking pictures and the various lenses and cameras gives me an impetus to shoot more with different pieces of glass and cameras.