Well, I'll just offer a little balanced perspective. If you look at the recommended daily set point for charging, it is not AT 90%; it is a section of battery range from 50% to 90%. Choose as you see fit. Considering that the car will start warning you that it's not a good idea if you set it for 91% or more, I don't see how 1% less than that is magically perfect. I use around 75 to 80% to keep it a little farther from that unrecommended area. Also, that is fine for us since most days we don't use more than about 20 or 30 miles, so it's never really low anyway, even if we've gone a day or two without plugging in. I do understand Tesla's recommending to keep it plugged in. It's a new experience for people if they are used to driving a gas car, and they want people to build that habit and have that range confidence, not forget for a few days and then they realize their car is low and they are stressed because they need to leave for work. Also, they do want to assure people that it is not at all bad to keep it plugged in as much as you want.
For the sudden emergency movie-scenario trip at 3AM, that might come up once in a decade or two, do you have Superchargers near you? If that were to come up, and my car isn't at 90% in the middle of the night because I have it set to start charging at 1AM, I have options. I can still probably make it to the Supercharger 2 hours away, or I could hit the Supercharger here in town for 5-10 minutes before heading out.