For Canon, 5 or less is probably the ideal number. I ordered 10 each of 2 different cameras split into orders of 2,8,4,6, and received all of them. However the 6 of another camera got auto-cancelled and the 4 of that same camera is just sitting there as "Order Received". I stupidly placed an order of 3 more of a camera I had already received 10 of and am now on Canon's no-go list apparently. Any order attempts to that address get an error at checkout saying to call customer service. Not sure what they block, but I'd assume shipping address and account at a minimum. They seem pretty aggressive so I wouldn't be surprised if they also block billing address. I hope that's not the case and would love to hear from someone who knows for sure. I don't mind burning this shipping address, but name and/or billing address would be more problematic.