My personal machine? My last one (a MBP) I purchased in early 2015, and then replaced it with an M1 Max in late 2022, so I ticked 7-8 years 
I plan on keeping this Mac for a decade or “until it breaks” - if I had my time again I probably would have bought a cheaper MBP so I could justify replacing it a bit sooner (given there’s already M2s and M3s and…), but ah well.
Work seems to be three or four years - I got a new 2019 MBP when I started there in early 2020, and it got replaced with a downcycled M1 about six months ago.
