[0] EDIT: for reference, my previous ThinkPad lasted me 14 years.
I ran a 2008 MBP until 2019. Then…gave it to my wife who used it until 2022. Finally retired it after the battery swelled. I suspect I could have replaced the battery and she could have got another couple of years out of it if I really needed.
Not once did that device ever feel obsolete.
Their recent hardware is proving much more capable as tools than the budget i5 I had before, so I upgraded. In terms of machinery expenses, it's more than I'd like to spend on RAM and ssd than I'd prefer (their pricing ladder is comical) but the product is amazing. I'm going to wait as long as possible before I upgrade to Tahoe though, seems almost DoA
If they're working perfectly, why does it matter if they have current operating support? It doesn't seem like you're dependent on Apple.