This question comes up over and over again. Just plug it in and let the battery management system manage the battery. The manual says this twice, in bold print. Setting the charge about 50% would be ideal, but it doesn't matter much what charge you set it at as long as it's not 100%.
"Remember, a connected Model S is a happy Model S," and now that applies to the Model X too.
If Tesla still put those cards in the cars it would save a lot of questions.