Hey wings,
About the airelons they activate simultaneously with differential in there movement so the one going down moves more then the one going up.
The amount of time a plane will stay in the air is not the engine speed but the capacity of the fuel tank. With an 8 oz. OS .40 LA i usually got about 12-15 minutes of flight time however id come down a bit early just to make sure i dont run out. If you think thats a short time its not and all you have to do to go up again is just refuel and start it up again.
Good luck,

Papa