Well it is silly and it isn't. I find the 15 posts per day more silly tbh, because there are a looooot of forums around here for shows that last 10 episodes a year, have 9 months of hiatus and maybe a couple of months of promo before they air so it's kinda silly to make them post a number for nothing, just to keep existing in between seasons.
However the 48 hours rule, I kinda get. Boards have two mods (well most of them
) and if they can't even be interested enough to make sure the board is not dead for 2 days, with two people, what's the point of having it at all?