I dunno, longer than 6 years, which is about how long it took for Skylake to go from brand new to not being supported by the new version of Windows?
And I honestly can't think of a time that's even happened before when you could get 10 running on 10+ year old processors as long as they were powerful enough. And the difference between a Core 2 Duo and a Skylake i7 is vastly more than between the Skylake i7 and the current generation.
The issue is not that the hardware stops getting support, either... It's that the hardware is expressly and needlessly being blocked long before it's no longer useful. My old Skylake is now 9 years old and more than capable of running as a moderate power machine on current workloads, other than being forcibly blocked to encourage me to put it in a landfill so I can continue the consumer march for more stuff to feed the corpos.
It's wasteful. And for the most part, all that's needed is for the old drivers to be allowed to function. And to make things like TPM 2 be optional, especially considering I don't think you're even required to actually use it for Windows 11, just have it.