What exactly does "heavy use" mean? My MacBook Pro is now in its fourth year of daily development work. It doesn't show any kind of wear. So far I don't see any reason to replace it in the years to come. If nothing major changes I think I'll get another four years out of it.

I’ve never replaced a MacBook because it was worn out, but because I wanted a newer, higher performance version. I have a 2018 MacBook Pro that I just can’t get rid of because it still works great.