It's TECHNICALLY Bad to charge to 100% and LEAVE IT THERE. I would not recommend that for longevity. A day or two, even a week or two here and there, really isn't going to make much a difference. YEARS can hurt the overall health & capacity.
That being said, I'm prepairing to finish a video I started in 2016, 7 years ago. I have 2 x 18650 Cells from a 2015 P85 with I think 15,000 miles on it. They were given to be my WK057 for testing.
After I finished my capacity tests, I decided to do a LONG term test. Since I had two cells, I charged one cell to 100% and the second cell I discharged to the approximate voltage a Model S would shut down at. I put both back into their storage case, and put them in a nice safe place, where I actually forgot about them (read, couldn't remember where I put them). Finally found them in my office while cleaning, dusted the case off. Initial voltage readings are GREAT! I started doing the final update to the video, and put a few cycles on each cell. Surprisingly, extremely little capacity loss. Thats not saying they haven't degraded in other ways, but initial results, very little capacity loss.
I still recommend around 50% SOC for long term storage. I in fact do this with with all my lithium batteries. Example of how well 50% works though, I got my first laptop on October 21, 1998. I actually STILL use it. It's running Windows 98 SE, has a ton of different ports, and communicates perfectly with no hassle with some old equipment I still work with, such as motor controllers, CNC machines and what not. I dabble all over the place. Oh, and it still runs some classic games that Windows 10 & up can't. Original battery, which got the crap used out of it back when that was my main/only computer in Middle School & part of High School, and then occasionally since. That original battery, still keeps the laptop powered for 2+ hrs. When new, I could get ~3 hrs run time per charge, if I wasn't using the dial up modem on my 200 ft phone line so I could sit anywhere in the house......
