I would say that this topic has been addressed more than dozens of times.
I'd also say that there is no consensus beyond keeping it between 10 and 90 percent charged.
The advice for "keeping it plugged it" is conflicted by the manufacturer's interest in avoiding any batteries discharged by long periods of not being plugged in, and resultant customer outrage.
The possible if minor cost of having all owners overcharge is less than the possible cost of having any one customer fail to charge adequately.
When we evaluate a source's credibility, we examine the expertise and the trustworthiness of the source. Tesla is certainly expert in its battery charging advice. On the second dimension, they do have a vested interest in never encountering a customer whose battery discharged from neglect, hence, probably, the advice to charge more than needed.
There is the likely definitive lecture by battery architect and chemist Professor Jeff Dahn
at 73 minutes. Watch this and pay attention please before asking us more about how long to charge your batteries.
If I were leaving for a long time, longer than 3 weeks, I would plug in my Ss and set them for some level between 30 and 70 percent charge. Three weeks, not to worry.
I could be wrong.