I try to stagger my stock, and there's a logical reason I do this...

Because there are a few pet food supply shops near me, I consider the 'what if' factor of my freezer breaking down, or a power cut happening and ruining what I have stored.

In this sort of worst case scenario where you have to discard considerable numbers of unusable, rotting rats that give off a delightful aroma, I hope to have to throw out less therefore wasting less money in the process.

If the supply shop is near enough, I'd ask why risk having to lose money and stock if something happens? Or, make sure you have something to back your freezers power up for 'x' amount of time if you lose mains power!