5-8 years probably
unless you are doing specialized workloads (encoding, inference, highly multithreaded sw), cpu perf won't make the biggest difference
I've been using a 2010 laptop for the past 7 years (ssd + ram upgraded at some point) and it ran everything that my current mbp runs basically the same 90% of the time. The other 10% is like running VM's, building android, or other stuff that I rarely do.