When I was a kid, I traded in my first salvo of gaming stuff when the generation changed. N64 came out, I was so desperate that I traded in my NES, Genesis, Game Boy and Game Gear at Funcoland. Although I long since got it all back. I've had the replacements for so long, I don't even remember where they came from and may as well be antiquity. I'd find this kind of stuff at tag sales, end up with many consoles, give some away to friends and family so they can experience Sonic, and just decided to hold on to at least one working version of each system.
I traded in the N64 after Dreamcast came out...desperate to afford a game. But then I had the chance to buy the clear blue Funtastic model later. I now have like 4 or 5 normal black ones too and I'm not even sure where all of them came from, just left behind from a forgotten age. I wish there were as many working 64 controllers as there were systems lol.
I let my PS4 go after PS4 Pro was announced, knowing what was bound to happen anyway. I had an original white 360 that broke, but never bothered getting it again. Series X is my first one since first gen 360.
I never had an original fat Game Boy again, I got the GBC instead. Now I like the SP. However, I NEVER parted with my 1991 SNES. Still have it. Confronted with N64 coming out I was willing to part with almost everything except this.
In hindsight? It would be kind of cool to have all the original hardware that I actually used back then, but trading in that stuff allowed me to both get the new gaming experience I was looking for when it mattered and learn a valuable lesson. And everything is readily available and easy to play these days, so it's a wash.
At some point, it stopped being worth holding onto every console iteration. That point was 360/PS3. Everything since then has just been a more powerful version of what came before. The switch to x86 really marked this. You would keep a PS4 and PS5 for the same reason you would keep an old PC and a new PC, because you want or need two. Not because the older system has some experience trapped on it.
This train of thought had me thinking though, if I get a PS5 I will probably let my sister take the Pro. Allowing me to take the base PS4 back...which I could then hook up to my CRT TV because it's the only Playstation that's currently supported with streaming apps that has a legacy A/V out (PS3 is dead). I think it would be pretty cool to see a PS4 driving a CRT, I kinda wanna try watching "normal TV" on it again, to say nothing of the benefits in any games. Moral of the story...I'm a fringe case, but don't get rid of anything after all LOL