Windows: In my experience, Windows PCs typically started to require a full reinstallation of the OS every 1–3 years; and were hardware obsolete in 2–4 years.

Mac: I switched fully to Mac in 2009 with a 13″ MacBook Pro. Apart from a battery that only holds 30 minutes of charge, I’ve quadrupled the RAM to 8GB and upgraded the HDD to a SSD. Apart from the battery, it runs better than new, and it’s nearly 8 years old now, though I mostly just use it as a spare living room / bedroom computer now.

My daily use computers are (a) a 13″ 2012 MacBook Pro that I use as my laptop, and (b) a 13″ 2013 MacBook Pro that’s permanently on my desk connected to a huge curved LG monitor.

Both of them run like the day I got them.

We also had an old 27″ 2010 iMac that similarly ran better than the day we got it, also thanks to increasing the RAM and doing the (tricky) SSD upgrade.

Net-net, in my actual, practical experience, it appears that Mac products typically have a zero-upgrade lifespan of easily 4–6 years; and an upgraded lifespan of 8+ years.

Whatever way you cut it, that is phenomenal.