I've had store stock site in Customs Hands for about 4 months.
Realize that ALL parcels go into a giant warehouse together and it can get to be a giant clusterf*ck and really hard to get through. Parcels upon parcels stacked everywhere. If your parcel came in with say a huge truck packed full then yours might be on the bottom of that pile.
Now if it also came from an airsoft dealer in Hong Kong then it's put into a maybe pile to be searched which take longer since parcels that are deemed not to be of notice are sent through first.
Now if they don't have enough people or allot of new people it takes them longer to go through those piles.
Also each pile is searched by a K9 unit, so if that unit smells something from the pile your parcel is in, expect to wait even longer.
The list goes on.