I gather the recommendation is to keep the M3 on its charger whenever its at home. If it is only being used 5-10miles a day, is it really better to charge all the time, every day? I would never do that with a phone, ipad or laptop. So not better to let it go down to say 40-50% over a few days then charge up to 80%?
The tesla manual, on page 122 in the version I have, specifically tells you there is no advantage to doing what I have bolded above. The car is not a phone. Also, just be aware that if you charge to 80% only, instead of 90%, you will likely see more "drift" in what the BMS reports as available range.
Doesnt mean you have an issue with the battery, and doesnt mean that 90% is "better" than 80%. It simply appears that charging to 90% regularly is easier for the car to see how much power it has stored than 80%.
if you are only using the car 5-10 miles a day, my suggestion would be to plug it in every time it hits your garage, but to have your max charge set to 70-80% and not care what the BMS (car) reports as "total" miles available, because it wont matter in the slightest to you.... because you only go 5-10 miles a day. Max range showing 240-or 250, or 290 or 280 has ZERO meaning when you go 5-10 miles a day. You wont be hurting your battery to charge every day, and have it set to some percentage lower than 90%, its just likely that your car will report shorter max 100% charge.
If you go on a trip somewhere, charge to whatever you need, even if thats 100%.
basically, plug in, set it to some percentage you are comfortable with, and ignore max range completely unless you are going on a trip.