A Note on Immortality
Many of the supporting cast of Besides the Will of Evil are, if not perfectly immortal, then at least functionally so. Celestia and Luna derive their immortality from their divinity- as do Cadence and Twilight, though the latter has not made use of her immortality yet, and the former may have, or may not have- the show does not give us clues to her age. The various powerful deer- Falalauria, Fëanor, the three red deer sisters, Nordeshang- have achieved functional immortality through their considerable magical power. Reiziger is immortal from the vein of black nothingness that runs out of him.
What must this be like? It is worth pondering, for a moment, on the timespans not merely in this story but in the show itself. While the Dangerous Business version of Equestria has been around for about two thousand years, the show's Equestria is at least a millennium old, and seems to be noticeably older if we take our cues from the settled nature of Celestia and Luna's rule in 'old time' episodes like “The Crystal Empire” and “Princess Twilight Sparkle.” On these notes, Celestia's commentary that she merely found it convenient to keep lying to her ponies seems, at first glance, incredulous. How convenient could it be to hide the truth for two thousand years?
Yet consider your own life. How much do your days and weeks and months run together? Time slips by like a rushing river. The weeks become months become years become decades. It is not a stretch to consider that the decades might become centuries, and the centuries millennia. Even with an infinity of time, it would seem that a lack of time becomes a problem. Indeed, with all the time in the world, a lack of time seems to grow more acute than it ever could with limited time. Moreover, even a small problem may become something that is put off with too much time. Imagine the temptation to put off a large problem indefinitely, until the ending of the world makes it no longer a problem at all?
None of this is to excuse Celestia and Luna's actions. I offer it merely for the sake of perspective. It is also a warning, I suppose, for the Mane Six, as they stand on the threshold of godhood and immortality themselves. Be wary, girls, of thinking you can deal with a problem later. Later may be too late.