I work from home and only use my Model 3 on the weekend. I set my charge level to 80% during the week and bump it to 90% if we are doing a Saturday roadtrip. My M3 is always plugged in. When it's full in the summer it's not pulling anything most of the time, it must turn on for a minute or so every now and then to account for phantom drain but that's not significant, so for all practical purposes that's the same as not having it plugged in.
Having it plugged in all the time is a convenience , when we have a weekend trip I can just bump the level up from the app without having to go outside.
In the winter having it plugged in is much more important, it has to keep the battery comfortable and that takes power. You can also precondition the car before going outside, that not only warms up the car for the passenger but it also keeps the side windows from sticking and melts the ice in the windshield.