I don't think there is really any kind of secret as to when you should order anything.  I think it really depends on how well something sells.  I think we have all done this once or twice... For some odd reason.. the POS system in my dept. doesn't work..hmm... so I have to place manual orders.  I seem to get a lot of stuff that I don't need.. example... I have an item on the shelf   8  total on hand including whats in the back  24 .  Now, there is 6 in transit, 6 in the warehouse and 6 on order... so does this make any sense ?  NO.  In the pets depts its a tough call.  If you are the one working your bins then you would know what you have and what your needs are.  Sometimes having a bit more overstock is a good thing.. which insures that you don't run out.

 

Also, I am finding that if I have an on hand count for something and I want to place another order.. I get a screen that asks me if I want to continue because with the new order and the current one will give me xxx amount.. which could in fact be the extra overstock that you are talking about.