I have voted 5-6 years for partially the same reason you cited: after this period I feel that the vendors have mostly abandoned the machines, especially Apple.
They have a generous policy to support devices for a long time but my Intel Mac has visibly slowed down at places and I know for a fact its thermals are fine. Apple just doesn’t bother as much with devices they internally (and secretly) consider obsolete. I have also noticed my iPhone 12 Pro Max getting detectably slower in the last 3-6 months (and the battery is still shown as Peak Performance) which really started making me weary, if not angry. Planned obsolescence is alive and well, sadly. The corporations understood it’s a bad PR to announce it openly so the next order of business is to do it surreptitiously… 
This is why I’ll gradually make a comeback to Linux. The laptop I have is actually fairly powerful and I know that for as long as the hardware is working well, Linux will keep it fast and reliable. Linux also doesn’t have (not by default) all the scanners and telemetry that Apple and Microsoft employ – in the case of Apple they literally scan every program after you start it which is resulting in a periodic lag when you work in the terminal for longer periods of time.
Macs have served their role in my career. I might buy a refurbished M1 or M2 on a low-mid configuration (i.e. with 16GB RAM so the OS does not trash the SSD and reduce its lifetime) because they are champions in battery life and are lightweight – I’ll need that when I start traveling and working on my own business(es). But outside of that I’m going full Linux (and I’ll be remoting into my home Linux machines with the Mac laptop as well; it’ll be a beautiful and lightweight thin client).
So if you make the same poll next year I am definitely voting “Until it breaks”. 
