

The amount of time the battery spends at higher voltage definitely affects its capacity over time. There’s plenty of research on Li-ion battery service life characteristics done with greater scientific rigor than is possible with batteries installed in phones.
It can take longer than the few months these tests required to see the effect. A phone that’s usually stored at 60% will eventually show a big capacity advantage over one that’s stored at 100%. That’s probably mostly true at 80% as well.
For some anecdata, my Pixel 4a has spent most of the past five years limited to 60%. It reports 1152 cycles and 91% capacity.












The advantage is that I can occasionally charge it to 80% or 100% if the situation demands it.