Well perhaps leaving your crypto on a gambling casino wallet is still good for a short period of time like a day or weeks, beyond that --that is too risky.
The problem here is that you don't know when a hack will happen. So, it doesn't really matter for how long you leave your cryptos on the casino. But, surely, the shorter the less risky! (
not your keys not your money).
The goud thing, though, is that the money used for gambling is supposed to be a money you can afford to lose and you are supposed to be aware of the risks involved.
On the other hand, I believe securing customers funds is mainly the responsibility of the casino. The least they can do is to have a hot/cold wallet setup. This way even if they get hacked most funds will remain safe and it won't result in their bankruptcy.
Well, that measure is a great idea, you can clearly see that what is safe is what works, if you take that idea I think they would be covering their backs in the face of any eventuality of hacks, and thus they can avoid a bad time, I don't know if the Famous casinos will have that security, because I understand that one of the things that a casino platform spends the most on is security.
Although there are currently few casinos that have experienced this type of attack and have been successful, that is why the 2FA security layer is always very necessary for users.