The 15" Aluminum PowerBook G4 that I got in 2003 died a year ago. Had not used it for a long time and got it out to play with some old PPC software. Was working fine, then it crashed and would not restart. All I got was a "chime of death" indicating a memory problem. Checked it out as well as I could, and I think it's really dead - no big deal, I don't need it.
My 2008 15" MacBook Pro still works but the battery died a couple years ago. Again, I don't need it and it just sits in the closet. The screen doesn't look so good anymore and it generally looks and feels old, but it still works.
My 2013 MBA is still my primary computer and I'm happy with it. So my Mac laptops tend to last much longer than needed. 🙂