Most likely he will use it as long as it's hidden and no one knows about it but mostly as well he will be found out. But as soon as he found out, he will be in trouble unless he knows how to disappear before that even happen. Because of greed, most people don't always stop when they find a loophole in gambling, they mostly abused the bugs in order to gain more money at the end of the day greed will hunt them and they will gonna lose their money because of that, just like what we heard from the stories of others.
As long as he could continue to use it, he would still use it for his own benefit. And if it is no longer useful, he will likely sell it to someone else for more money. But the casino will check every system in the casino and immediately close the bug if there is one. The casino will also know if someone is trying to use it for its benefit and will either block the account or not process the withdrawal. But it's different if the casino holds a contest to find bugs, it will make people compete to find the bug and report it to the casino to get the prize.