But I can't imagine my charging behavior is that different than most people that would plug in their car regularly, and it seems most people have had much better experience with degradation? There can't be that many people setting their charge limit to 50%
Some do, with very good results for degradation.
I sold my 2021 M3P after 66K km / 41K mi and 2.5 years and had ~5% from the full pack when new(most batteries starts and newer exceeds 80.5kWh for that so in that only a few percent degradation.
Range wise, 492 km out of 507km new when I sold it.
Calendar aging causes the most part of the degradation and it reduces rapidly so another 2.5 years would maybe have put it at 4.5% at fice years age.
So the question i have then is, should I just stick to 90% and hope the battery degrades enough to hit the warranty replacement, or do I just need to set the charge limit way lower and cross my fingers that i get another 5-10 years out of it?
Calendar aging is what took the absolutely biggest part of your battery. You have not even many miles on it.
Keeping 90% in an average climate would ”cost about 6%* the first year in degradation from calendar aging.
After four tears from new 6% is doubled to 12%, and after five years about 13.5%.
This is from time at high SOC only.
I do not know the climate in Seattle but not too warm I guess?
The prognosis for the degradation at 8 years age of the car is about 21.5% degradation, assuming the BMS is correct and the 17% of today is correct. This is if continuing to using 90% as you do today.
Calendar aging from cells taken from a ’18 or ’19 model 3. (Panasonic 2170 cells)