Bought a Mac Pro 1,1 in 2006, used it daily until 2020 when I finally replaced it with a s/h MacMini because it no longer worked with stuff like cameras, and none of the softwares could be updated. So around 14 years. It had new optical drives, HDDs got swapped for larger ones as they became available, graphics card had to be changed when the original went kaput, but largely in 'original' condition. Oh and I added more RAM. Because, more RAM. I paid probably around £3000 over it's lifespan, which I think is pretty good value really. It now sadly languishes in its original box in the basement, awaiting a new loving owner. If I can find one.
I also have my first ever Mac, a G3 iMac Summer 2000 DV+ edition in Indigo Blue. I haven't used that in well over a decade though, so not sure it'll even turn on now. Can't bring myself to get rid of it, even though it takes up a lot of space.