I don`t think that there is any amount of winning that can propel a gambler to stop gambling. The more you win, the more you want to continue playing to win even more. This is common among gamblers. Even when people lose continuously they continue gambling so how much more when they are winning? They will continue.
Many who won millions in gambling usually set up businesses as you have mentioned but that didn`t stop them from gambling. Gambling has been made in such a way that you can lie on your bed and gamble and so this ease of assessment has also made it difficult for people to stop gambling. I can make a pronouncement that I will not gamble again but then it takes very little thing to take me back to gambling especially when I remember the good old days.
I don`t advocate that people should stop gambling or retire at a certain age because the reason we gamble differs from individual to individual regardless of age. Some have fun through it, Some try to make mega money through it, and others use it even as a coping mechanism. So, if the old person is gambling for a justified reason we can only hope he gambles responsibly and controls his emotions because at that age they are easily prone to high blood pressure and his inability to control and guide his losses might result in that.
Yes, that's true because once a person wins, he will imagine how it would feel if he could win once again an even bigger amount of money. It would be fun for him because he could earn even more money. They will not really stop gambling and leave gambling forever because they have experienced getting a big win so there is a desire to gamble again to get an even bigger win. But in reality, they will still find it difficult to win again.
Those who can win millions in gambling and can set up a business and grow it bigger should no longer need to think about gambling because they can already make money from their business. Maybe he can go back to gambling, but there is no need to use a lot of money because, at that time, they should be able to think of gambling as entertainment and not to make money. They must realize that it will be difficult for them to win millions more from gambling so they should focus on their business and think about how to grow their business even bigger.
People need to determine when they can retire from gambling so that when they decide actually to retire from gambling, they don't do it by force but because they are aware that they no longer need to gamble. But only a few can have such awareness, while others still try to gamble to win a lot of money. Indeed, leaving gambling forever requires strong effort because of the pleasure they get from gambling, so they still want to return to gambling after stopping for a while. There is a desire to repeat the times when they could get that pleasure and they want to know if anything has changed about gambling so that they end up going back to gambling again.