I learned my lesson after the 2005-2006 conversion to Intel. I got the last iBook (my first Mac!) that was PPC and saw how fast the transition was supposed to happen, and how it actually happened and how PPC languished once the white Intel Macbooks were around. Apple couldn't drop those fast enough with all the topcase chipping. I wouldn't doubt too the M1 will have a shorter support cycle than the future M series processors as it was the first. Apple seemed to have done this for the first of any generation product. It's like it is an expensive prototype. I bet like the whole Intel cycle, the M processor will go back to a longer support cycle as the transition is almost totally over (are there any Intel processors in the lineup?)
I do have a 2013 i3 Win machine that is on Windows 10. So it's supported to 2025, but it's honestly getting laggy even with just a browser despite an SSD and 16 GB RAM. So it probably will have 10+ years of life (I bought it for less than $300 new back then, so it was at the tail end of processor and machine series lifecycle anyway) but it is sucking at the end of its life. At almost 10 years it's really when I feel any computer gets old, unless it's for a parent and they only use it for very basic stuff. I'm going to put some type of Linux on it after Win 10 isn't supported. I only really use it sparingly and take it on vacation as I don't care what happens to it. I just basically need a browser.
As other people mentioned just because it's old too doesn't mean it's dead. My other half is still using a 2011 13" MacBook Pro and it fine with it, performance isn't horrible. If it works for your needs, just go with it.
I am glad I avoided the last decade of Intel machines anyway, they seemed like a mess. I went from a refurb 2008 15" Pro, to a mid 2012 13" Pro (there was no way I would buy that last generation of laptop keyboard, and it was the last machine you could upgrade yourself!).