Honestly I don't know like most of the other gamblers,because we may win many times but still wanted to gamble so any amount can't make us to stop from betting but if someone really new to betting but they won in few millions then they might quit gambling for a reason.
I think you should determine on how much you have to win to stop. Because if you don't know how much or you don't have an idea when you should stop, this is going to the point of addiction.
Winning millions with gambling is a very rare case, I would actually quit if that happens to me although there were gamblers that experienced this. I wonder on how they're doing right now.
I feel setting up a target reward to win from gambling will make us more addicted,so just play and enjoying the moment will keep the things simple and also avoid gambling thougts in our daily life routine.Winning millions is rare case but I never seen anyone left their gambling habit even after they won in millions,they will spend all the money for betting in the process of making billions so quitting never related to the reward amount.