There is a lot of gambling site now are instant withdraw because as a player Im looking also for that. But now I don't they have some gambling site who have need more hours before payout sent almost gambling site now are instant withdrawal . Best example for that is Stake after requesting payout they sent it directly to your account instant no waiting needed.
It is always nice to get the withdrawals instantly when we raise the request for it. Most of the gambling sites process the request instantly. Sometime I see a delay of 1 or 2 Hours in withdrawal processing in few sites, which is acceptable.
Delaying withdrawal process because maybe they have some technical problems and yes it is acceptable but the important with that when we almost requesting to payout from the gambling site they sent payout directly to our wallet waiting few minutes the confirmation is mostly is very slow why we cannot use our bitcoin.