it depends on customs for your country, stock available from the distributors(many photographic companies have a middle-man between the store selling and the company making). Also, the speed on how fast the order is phoned in to the distributor, company direct, etc....
some companies, such as here in the US, Kodak in particular, you have to have a minimum order amount ($ wise at least) when you order from them as a retailer.
having worked in a retail job selling photo supplies and film all day long, I feel your pain. I had customers who shot 8x10 and 5x7 TMAX and Portra (not normally stocked items at the store, but S/O), and it would take usually 4-5 weeks or so. Generally, they were ok with it, cause they were ordering a lot of film at a time. Especially the 5x7 color neg. That stuff was hard to get.
-Dan