Yes, that's correct! The entire balance is recycled and any staked HASH are recycled as well. The process is automatic. This is mainly happening to people who came to test the platform and have there a few cents or dollars left. The main stakers of the platform are using their own EOS wallets.
Do you mean in order for our account not to be purged we'll have to withdraw our HASH out to our personal wallet? How do we stake them?
This makes the clients go away from your casino really. What constitutes being inactive that you consider purging, is it when they stop playing, or if the account stops logging in?
You need to bet with your account at least once
We don't have any clients who are staking any noticeable amounts without using the accounts regularly. They can't go away and stop playing if their accounts are recycled for not being used for more for a very long period of time 
