It's not a question about amount. If you have made a huge deposit it mean a Trade Group make a huge profit with your deposit, so it have funds to pay you (but you make a payment request for us, and then we have to withdraw funds from a Trade Group internal account). So first of all it's a question about time.
We keep 15-30% of our total funds in our hot BTC wallet. If withdrawal amount is bigger than amount in hot wallet, so additional funds should be transfered from our cold (offline) BTC wallet.
If you want to withdraw PerfectMoney, AdvCash, Payeer we don't store a lot of funds there (as funds can be frozen with or without any reason there). Thus, we need to convert BTC to these payment systems first.
If you want to withdtaw huge amount, it can take up to 6-12 hours. Usually we pay in 2-3 hours after request.