How up-to-date are Amazon MWS reports?

Question

I have the following problem: I updated my products via Amazon's MWS API (using PHP - _POST_PRODUCT_DATA_ and _POST_INVENTORY_AVAILABILITY_DATA_). I deleted one product and updated the available quantity for another product. After both feeds have been processed (wihtout errors) I requested a report of all my listings (_GET_MERCHANT_LISTINGS_ALL_DATA_). This report did not contain any of the changes I made. After about an hour, the quantity change showed up in another report, the deleted product still appeared. After I changed the quantity back, the same thing happened (the first "changed" quantity still showed up.

Within the sellercentral, everything's fine - the quantity is updated rightaway after a feed is processed and deleted products also no longer show up.

So I'm wondering: how up-to-date are Amazon's MWS reports? I was actually expecting realtime information when requesting a report and finding out that's not the case is causing me quite some problems now.