I'm also using a 2012 MacBook Air that still runs as well as it did on day 1. I have an additional monitor, magic mouse and keyboard that makes it as usable as a desktop computer when home. Clearly Apple over engineered these laptops because most technology today is designed with planned obsolescence. I also recently bought a 2020 iMac for the kids, I can flit interchangeably between them and wouldn't know the difference. I also worry a lot less about viruses and haven't had it crash once yet.
Equally, for the same money I could have probably bought multiple cheap laptops and replaced them every 3 years.