Cryptocurrency withdrawal times can vary due to block confirmations (various cryptocurrencies have longer block confirmations). Further, if the network is experiencing high network activity then confirmation times, and subsequently the withdrawals can take even longer.
In addition, Gatecoin only keeps a small percentage of its user funds on its secured servers for instant transfers, as a security feature. When we receive an increase in withdrawal requests, those server funds can run empty, which means that we need to manually refill them. This process takes time: usually 1h for BTC and 20min for ETH and ERC20 tokens during office hours, and it can take up to several hours at night or during weekends.