When looking at the discharge curve of just about any 18650 cell, there is no extra range between 4.1V and 4.2V. The 4.2V number is listed as max charge, but...that is only because it is capable of taking a charge to 4.2V, it doesn't mean its a good idea. Since I found this out, I haven't charged to 4.2V under any conditions, ESPECIALLY when storing over the winter (meaning I make certain I don't even accidentally use 4.2V).
So then...the question becomes, charge to 4.1V (90%) or 4.05V (80%?). I understand the desire to buy the smallest, lightest, and least expensive battery that will "do the job", so then...there is a pressure to charge as high as possible, to get the max miles for the next ride. I've bought four ebike batteries, and so far I've sold one, the oldest and smallest, from back when I wanted to make sure it would fit any bike I'd ever get.
Then, I suddenly found myself getting some overtime at work, and I bought my dream street commuter, a $700 stretch cruiser. Huge triangle space, and comfortable riding position. Right now I have the biggest battery I could find at the time of purchase, 24-Ah. On my longest rides, I never run out of juice, so now?...I charge to 4.0V per cell, and I still never hit LVC...I have no way to prove this protocol will make the pack last twice as long, but...I believe the posted recommendations from Tesla, so that's what I'm doing.