The two Princesses that Faust has named Celestia and Luna may be way the hell more powerful than we take for granted. So, here's a question for you: Aren't Celestia and Luna actually spinning the planet every time they so-called "raise" the sun and moon?
The only reason those two things seem to move in a straight arc across the sky is because we're the ones who are spinning while they stay stationary. Okay, the moon moves too, but it's only revolving and doesn't rotate.
See, in order for Celestia to lift and drop the Sun, she would have to spin planet earth 180 degrees every time for the western and eastern hemispheres to get their light, and for the sun to appear to move across the sky every day, (a magical job she would have to keep up every minute of her waking life; even when her horn isn't lit up. She still controls where the sun is in relation to earth, even during the night). Not only that, she would need to keep track of the planet's revolution around the sun to make sure that the seasons happen at the right times, so that the Pegasi don't bring winter in the middle of July and vise versa.
And Luna would need to not only be in tune with the rotation/revolution of the planet to predict where the Moon is in its revolution around earth, but she would also need to have magic powerful enough to control the proximity of the moon to the earth so that it doesn't escape gravity entirely or smash into the planet. AND Luna has to control the Earth's rotation for many hours at night to make sure the moon keeps on its correct arc across the sky Every single night.
So you see, these are two extremely wickedly powerful ladies. They're practically goddesses, and not princesses. I know Hasbro wanted them to have that title so they'd be more marketable to kids, but when you really think about it, they are freaking strong!
So it's really no wonder Celestia did not hesitate to banish Luna when she turned into Nightmare Moon. Nightmare would've had the power and then some to drive the moon into Earth if she wanted, destroying everything. Yeah she'd just kill herself too, but that's the kind of power Luna has. (The reason she took 1,000 tears to return from banishment is that it just took that long for Luna's immense power to slowly seep back into her blood.)
Or why it was so horrible when Tirek gained all the alicorn magic. If Tirek truly succeeded, he could've potentially had control of Earth, the Sun and Moon, all animal races on Earth and maybe the very Cosmos themselves.
This could also explain part of why Luna and Celestia entrusted the elements to the Mane Six; the Royal Sisters are ancient and probably starting to grow exhausted from their never ending jobs. They needed several young and able bodied ponies to take on such a massive role as defending the Earth while they helped keep the Cosmos in natural order.
Keep this in mind, and maybe think twice before calling either of them "lazy" or too "stereotypical" as princesses. It's no wonder Twilight asked if there was s book she needed to read to know about being a princess. It's one helluva big job.