While we're on the subject, can anyone tell me how eggs are ordered in the display?

I don't buy incubators, I always hatch the upper left egg, and I have two 7k eggs that have been somewhere in the middle for months. Clearly some re-sorting is going on, but I have no idea how.

I read somewhere that it's based on your current distance from where you got the egg, but that doesn't seem true because I recently went on vacation and the eggs I picked up there are not at the end of the list. In fact, I just picked one of them to hatch yesterday from the upper left spot, and now I see one of the vacation eggs in the bottom middle spot, with local eggs in both the left and right bottom spots.