2. Endurance is not affected by altitude?
Another aspect is that you use up a lot of fuel while climbing at full power to high altitude. For a flight at low altitude, you can throttle back to a low cruise power setting much sooner after takeoff.
Even so, the difference in endurance for something simple like the C172 is minute; we're talking less than 20 mins on a 6 - 7 hour flight. Either way, that's far longer than my boredom limit...
