After a hundreds hours of gambling I found out that it's pretty hard to stop playing. Gambling becomes a strong addiction and has a negative impact on other aspects of life. I have tried to control myself over and over again and found out that the best way is to make a long pause to let your mind relax.
I think the best way for you is not just pausing but totally stopping for a while. You are getting addicted to it due to long hours of gambling. That is a bad thing. Quit while you are still in control. It would be harder to stop if you are full on addicted to gambling already.
I am afraid that he will difficult to stop for a while because he found out that playing gambling is fun and he continues to play. I think he will need to ask his friends or his family always to drag him to get out of the place. Or if he plays in his room, he needs to have a friend who can ask him to leave from his room so he can stop from playing gambling.