So I'm not sure but I probably started collecting and building somewhere in the early to mid 2k's or so. I was never in it for the retro-feels. It was something slightly different to me as I, back then, felt like old computers were seen as trash and useless and I was like "why throw away an item that still functions perfectly?". That and I was always into playing somewhat older games anyway, so this fit my new hobby quite well 😜
For me the collection is essentially the reserve bank for spare parts, my intention has always been to build and not to have for FOMO or something. I never cared much for, well...collecting? I never even call it a collection, I just call it "my stash of spare parts" because that's what they've always been for me.
At first I started by dumpsterdiving and asking around if anyone had an old computer I could have. Later on I started visiting fleamarkets and other places where lots of old hardware could be found and I started buying stuff online and I gradually became (somewhat xD) more picky. But most of my collection is basically the lower and midrange stuff with some higher end gear mixed in here and there.
I also don't know when exactly I stopped buying stuff but it was also a gradual process. At some point I was just looking at my collection and I felt satisfied, with no 'hunger for more' or the need to get more. That and I also gradually had less and less spare money to spend on the hobby and I got into different things.
I never fully stopped buying things locally though, so new stuff did keep dripping in but at way lower volumes.
However, the itch to build more (retro) computers was never gone completely, but I simply have other priorities.
I did consider getting rid of most of it a few times but I'm glad I never did 😀
Still the thought has never completely left my mind to, eventually, start slowly selling some stuff in very low volumes, if only because it seems interesting in a way. But only if I feel like I want to commit, because I know selling this stuff will eat a large amount of my time and will require substantial effort, both which I currently don't have to spare as I have important stuff going on for the forseeable time.