I still use my early-2004 15" Thinkpad T42p, fully up-to-date on the newest OS (Debian Sid) release. It is showing its age - mostly when browsing JS-encumbered sites - but still gets the job done. I have never had to worry about my T42p simply failing to work due to OS compatibility issues.

Of course this machine was expensive when new, just like Apple-branded hardware is expensive. Sometimes all that money buys you something worthwhile like your 7 year old MBP or my 13 year old T42p. Other times it is just a lot of money down the drain like I expect the recent touch-strip-addled MBP series or any machine which has consumables glued in-place to keep pesky users from getting a few more years out of their investments.