because the 2019 keyboard is prone to heat issues, while the 2020 keyboard is not, heat related keyboard failure is not well documented, since most folks just blame crumbs or other cause, but it does exist.but that's not for everyone. and again, the base model only has 1 fan which is going to exacerbate heat issues.
I've seen a base model 2020 stay at 6000rpm and 90celsius by just video calling via Zoom.
or watching youtube on an external display (not even 4K).
my experience with the 2019 was similar and I was very happy to not have any of those issues on the 2020 4-port.
since the 2020 4-port runs a little bit warmer than the 2019 4-port, I don't see why the 2019 should be avoided at all costs.
the keyboard experience is completely subjective and the 4-year Apple program offsets some of the negatives.
I'm not going to suggest pretending to have keyboard issues just to get battery replacements of course, but 4 years is a long time especially considering ARM is coming.
4 years from now I'd expect a lot more progress in terms of power than the last 4 years have been with Intel.
the number of years you keep your laptop is up to the individual. the reason why i dont mind dropping 2-3k on a mac cause i expect them to last a long time, i on avg use my macs for 6-8 years before upgrading. thats why im still typing on my 2015 mbp. if your telling me my mac is build only for 4 years, i rather go buy a cheaper window laptop with same or better spec for much much less, and just upgrade more frequently.