Over gambling is something that is not encouraged. Everything, needs to be moderated. Too much of everything is not good and it leads to addiction. I do not support a fixed time for gambling, but naturally flowing with gambling is cool until when you are tired. If it is only 10 mins and you feel to stop gambling for the day, stop. If you are going 2 hours and still energetic and fun, you can continue gambling and will be cool.
I agree with you, in this case things should be very simple, do not play excessively, just play or kill time with just enough money to not spend more than we should, addiction is one of the most difficult things a person can go through, any of us should take care of that, I think that what can be Common in all players is that we want to play and win, but we must learn to accept when we lose to not fall into addiction errors.
Yes of course, gambling is not a job and doesn't deserve allocation of too much time. It is just like going to field to play ball and reaching there, you spend 4hrs playing football, will the fun still be there? So, while gambling, do not also put your mind there often, thinking about gambling every time will get you addicted.
What you think about very often will build part of your life and that when that happens, it is the addiction we are talking about. It happens gradually without the knowledge of the victim.