Would the moon ever need a "boost"? Even though it's probably not hitting any air molecules from Earth, it's still colliding with tons of space debris a day.
The moon is being continually boosted by the rotation of the earth. The moon's gravity causes tides on the earth's surface. However, the shape of the earth is slightly ahead of being directly lined up with the moon because of inertia and sloshing. That uneven earth shape exerts a slightly uneven pull on the moon which increases its angular velocity around the earth, and slows down the angular velocity of the earth's rotation.