Strutz Strutz:
There is getting to be a traffic jam up there!
I have seen orbits between Earth-Moon and Earth-Mars that are stable and use no fuel, and keep spacecraft running all the time between those points. Earth-Moon is about a week, Earth-Mars about 3 years. Then when they get near, another craft rendezvous and offloads passengers, and more board.
One day it will be like taking a long cruise.