I know RC and real flying are different but in the area of throttle management, I fly my rc planes just like I fly the fullsize ones. And that is, I use maxium throttle (or close to it) at takeoff and climb to altitude (or first turn). Then I reduce the throttle to a cruise setting which is usually about halfway on the fullsize and on my rc planes. Takeoff needs full throttle because while the airplane is on the ground it's a car and it's fighting rolling and wind resitence together. Once the wheels break free, the rolling resitance is removed and the energy used to break the rolling resitence will be converted to the energy for the aircraft to climb. A properly trimmed aircraft (real and rc) should be able to cruise along nicely at about half throttle (or slightly more) with no problems (accounting for wind, etc). Above cruise setting is so that you can climb. Remember, pointing the nose of an airplane upward is only part of how it climbs. The other part (which is the bigger part) is moving more air over the wings to create more lift. So that extra throttle past a cruise setting is so you can go up. The best example is a simple loop. You have to add throttle to enter one from level flight in most cases. Also, having some in reserve helps you get out of bad situations.