Really good question.
After talking to most of the drivers on our visits.
Not that many people tip them.
They consider the Maybach part of the package.
Most people that are on the "higher end" are really stingy.

FYI:
The 18% applies to "all room service" items. So think about that if you are going to tip the butler. Leave him something at the end of your visit is more
common and acceptable.


I usually tipped about $ 50.00 per Maybach trip
What a normal limo would cost us. And the drivers will make a
side trip and really help out when they know you better.

The Maybach ride is a gas. One of the finest and deceptively
faster cars in the world.
If its daytime
Make sure you use the LCD overhead sun shade.
Bring some champagne and put it in the rear fridge between the seats.
Heads will turn at the airport when you load up in that car.

Enjoy