We used to have earbuds that don't need to be charged because they had a headphone jack, didn't get lost so easily because they had a cord attached to a headphone jack, never lost the bluetooth connection because they had a headphone jack, and they cost less because they had a headphone jack. https://bsky.app/profile/daisyfm.bsky.social/post/3l3mfjc6sn62k
It is minimum of 5 years on AVERAGE for lithium batteries.
The way you charge does not change the average.
Yes it does because no manufacturer claims the lifespan in years, they say you get 2000 charging cycles. The 5 year number is derived from 2000 / 365 = 5.48 and that assumes you are charging them fully every day.
Look buddy, I'm not a battery expert and I can tell you aren't either. You can't get an easy number because the chemistry is complex and the way you use them changes things. When you do get a nice clean year number it depends on many things so making broad proclamations isn't very useful.