I did a quick check on Macbook Pros: * 10.8 (2012) dropped support for original Core 2 Duo (2006) — 6 years * 10.12 (2016) dropped support for 2009 MacBook Pr

I did a quick check on Macbook Pros: * 10.8 (2012) dropped support for original Core 2 Duo (2006) — 6 years * 10.12 (2016) dropped support for 2009 MacBook Pro — 7 years * 10.14 (2018) dropped support for 2011 MacBook Pro — 7 years The releases in between didn't drop support for any (mbp) hardware. The longest support I found with a spot-check was: * 10.12 (2016) dropped support for 2007 MacBook Pro — 9 years Apple tends to release updates for about 3 years for each OS. 10.11 (2015) got its last patch in 2018. 10.12 (2016) got an update in January and is expected to receive updates through September. I should have looked up desktops, since that's what most of the discussion is in this thread, but I don't have much firsthand experience with them. So assuming you buy the hardware the day its released, you can expect to have the newest software support for 6-9 years and have security updates for 9-12 years.