todge, i'm not sure if 100 hrs in 18 days is poss, but it is allowed. for it to work it would have to be very stress free otherwise most people would collapse after5 days of planning, decision making, turbulence, etc!
the arrow i was flying had a 70USG tank giving 7.5hrs endurance @9usg/hr!! i still considor 3 hrs to be a long flight. besides, even in the states, a 6 hour flight is going to be expensive!!