Some people probably have some write-off system, or perhaps resell them why the devices still have some value so they always are somewhere 'in the middle'.
I personally tend to keep my most recent device and the new device at the same time for about 2 years because of vendor lag (happens a lot with those classical software vendors that take months between software releases) and because I need the ability to compare between versions of both hardware and software. The newest device gets promoted daily driver (usually many benefits there, as they often are lighter yet more powerful). In general it means 2.25-ish devices per 10 years.
Other hardware, like SBCs tend to rotate out slower, but generic x86 platforms rotate out faster because if a critical component fails the labour for finding parts and replacing them is too much vs. buying up to date replacements. Luckily, due to lower usage of those machines they last longer, so technically the Apple hardware made the non-Apple hardware have a longer lifecycle in my case.
There is some irony in there as I do provide board-level repairs and the machines I work on for other people are ones I'd never personally invest in.
I personally tend to keep my most recent device and the new device at the same time for about 2 years because of vendor lag (happens a lot with those classical software vendors that take months between software releases) and because I need the ability to compare between versions of both hardware and software. The newest device gets promoted daily driver (usually many benefits there, as they often are lighter yet more powerful). In general it means 2.25-ish devices per 10 years.
Other hardware, like SBCs tend to rotate out slower, but generic x86 platforms rotate out faster because if a critical component fails the labour for finding parts and replacing them is too much vs. buying up to date replacements. Luckily, due to lower usage of those machines they last longer, so technically the Apple hardware made the non-Apple hardware have a longer lifecycle in my case.
There is some irony in there as I do provide board-level repairs and the machines I work on for other people are ones I'd never personally invest in.