It should not be about how long you have waited in minutes/hour but it should be related to how much you spend for the tx fee and about the deposit policy of the site (how many confirmation needed to get your deposit be credited on your account). Always check your transaction first whether it is already confirmed or not yet by the network. Dont complain just because you have waited for 20 minutes or more but you do not make sure your deposit confirmation.
The main question is, why was the BTC coin chosen as the main coin for deposits? After all, we all know that this network takes a large Commission per transaction and works quite slowly.