My desktop is a 2012 iMac that I got second hand in 2015. One RAM and spinny->SSD upgrade a few years after, and it's been going well since.
My personal laptop is a Dell XPS 13 that I think is now 10 years old and has never had an upgrade.
On both those, I don't keep any data for long before making sure it's backed up - I'm expecting a disk failure soon. Also the fan on the iMac makes audible spinny noises. But backups are good practice anyway, so that's a win.
I only just stopped using an external monitor that was so old it had a sticker on the front proudly boasting it had a HDMI port - fancy!
There are comments about investing in your tools here - and I think it's a balance. Yes, if you don't have the right tools your work will suffer. But the skills it takes to keep something running can themselves be valuable. And reducing e-waste is a good thing for many reasons, such as the climate crisis.
Away from computing, I just upgraded to a Canon mirrorless camera. A second hand shop had a body only model for way cheaper than it should be. I took a chance and got it, because I've seen their pricing go very weird on niche items before and I reckoned this was a similar case. (Most people looking for a camera from that shop would be after one with a lens - the seller should really have picked a different place to sell.) Turns out the sensor was filthy - but one cleaning kit later and it's doing fine.