The thing that makes older iMacs "disposable" is that the required cooling vents end up [mostly] blocked, within just a few years – then they thermally throttle, until death.
If you open them up and keep them clean, they can have uses forever:
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My 27" iMac (2009) still sits faithfully alongside my main 48" setup (because I own the copy of CS4 installed upon it – FU Adobe!). It mostly plays background shows (while I work on main computer, adjacent).
My 24" iMac (2006) still sits faithfully on my tax desk, for its annual usage/filing. It also still plays Warcraft 3: Frozen Throne (quite well!).
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>I suggest spending a bit more and getting a mac mini and a ... display, instead
This is fantastic advice; my past two Apple's have been Mini's. My three main machines all connect to the same massive 48" display (that is about to outlast its first retired Mini).
The only new iMac I would ever again consider purchasing would be something on-par with the iMac Pro (2017) – but in 2026+ any iMac would need a 32"+ display (minimum) to be "usable" IMHO.
Yeah and the old ones are actually pretty easy to open up. You just take a suction cup and clip the screen off.
I mean even the newer ones aren't bad but cutting the tape, cleaning up and putting new tape is kinda annoying. They should have stuck with the magnets.