To clarify, the question really is.. how much more degradation am I to expect if I charge to 100% quite often and leaving it say just over 90% for a day or two?
I don't want to kill the car and I'm not planning to abuse it just because it's a lease.
Had it to stop charging at 85% on a public charger earlier but I was going to be a few more hours than planned, so I just thought ah well may as well go to 100%.
If it's say extra few % degradation over a couple years then that's fine but if it's a serious issue then naturally I won't.
That’s the wrong question.
Lithium ion cells suffer from chemical reactions at high states of charge, which do a couple things. The battery cell contains what is called a “jelly roll” basically two sheets of rolled up metal foil, one copper, one aluminium, both are coated with a thin layer of a paste containing the lithium, nickel, manganese, cobalt, etc. If you charge to 100 it begins to cause cracking and other damage in this paste, the more cracks it gets the less energy it can store. There is a secondary issue if something called dendrites which is a process where the chemicals deform and grow spikes, these spikes can pierce the foils in the jellyroll, not only is this bad, it’s potentially dangerous and can lead in very rare and extreme cases can lead to battery short circuits and/or fires.
Tesla themselves, and almost every other vehicle manufacture explicitly recommend
not charging to 100% unless needed for a road trip for this exact reason. The same reason Apple have implemented a smart charging process for iPhones where once it has worked out what time you wake up in the morning, it’ll only charge to 80% overnight, then a short while before you wake will charge to 100% so that the battery spends as little time as possible at that maximum charge which
will cause problems with accelerated degradation. How much that is is impossible to put a generic number on, it’ll depend if you’re doing it at a supercharger or at home, if you’re leaving it a 100% for a day or a week. regardless, however you do it your battery will degrade faster that someone charging to 80%. Furthermore, it‘s just a waste of time. Above 90% you’ll get a max 50kWh charge rate, so if you’re clogging up a fast charger at a slow speed, it’s just poor etiquette.
Just follow the recommendation of the manufacturer and charge to max 90 unless you need it for a long journey. If as per your original post you're having issues with that because of your OCD, that’s a different issue to discuss with your healthcare professionals.