I'd trade my Yosemite-running '09 MacBook Pro but it still works fine (though it's probably coming due for a battery replacement).
It just refuses to die.
I have passed down probably 8-10 Macs to my kids and grandkids. I like to buy the new ones with new features ever 3 or 4 years.
All of these Macs are still working, and still being used. They can be updated when a new system comes out, and I keep mine updated.
I feel the same way about my 2007 IMac. Still runs like a champ. Never could have gotten this much use out of a PC.