I was in this for a few months earlier but gave up. Nothing to do with the service, it was fine. Just too much work and time to eke out a profit. It isn´t enough to earn payouts you also need to preserve the capital. The obvious approach was to sell tops and buy more hash lower. But that meant some idle cash that didn´t mine while waiting for a buying opportunity. It was a speculation. This was before S7, maybe things are different now. Anyway, eventually I got tired of this and got out with a modest profit.
These days it is even worse. While the hash has lost over 40- 80% of their value it makes no sense buying it.
Also giving a max withdrawal amount of 10 BTC is just wrong. It is the reason why we want to leave the banks. Putting limits on your own capital.
With 2FA (half of the times it don't work on their site or even withdrawals), it should be safe to withdraw all of your btc.
Your operating on the assumption that you send your money there and it just sits in an account waiting for you to withdraw it. That is not how it works. Bitmain invests into miners and equipment, which is used to generate a profit and pay interest/cover expenses.
The limit is to protect everyone from a big player withdrawing all available funds. Then you wouldn't be able to withdraw anything, since funds would be wiped out.
It is a good way to limit withdraws and allow everyone to withdraw a fairly large sum of money when they want. If you want access to your funds at all times, keep them in a wallet on your computer.