Greed is on our emotions which we can not control. Only a few people can control their emotions which is specifically called greed. And this type of people is too low. But those who can control emotion as well as greed are the perfect person and we have to follow them. And I think only they can quite when then want to.
One can actually overcome greed in gambling but it requires self moderation and discipline and constant practice. When one constantly practice an act, it becomes a habit and only when a gambler build those habit can he or she be able to overcome greed.
Well, maybe experienced gamblers should be better at controlling their emotions and greed and thus, experienced gamblers do not mean that it will be easy to win but more about having good control and discipline. Because at least, so far there are those who assume experienced gamblers will have good skills to be able to win in gambling, but I think the reality is not so. So yes, when experienced gamblers have discipline then it will be very possible for them to be able to stop when they get a winning streak, it would be impressive of course so as not to end up losing.