"Knowing when to play the lottery is relatively clear. You play when the expected value of a ticket is more than the cost. The Kelly criterion tells you how much to play by calculating what fraction of your bankroll you should bet when the odds are in your favour. Generally, betting more than twice the Kelly fraction will eventually lead to gambler’s ruin, even if the odds are in your favour" - Isaac Hepworth from Bookmarklet

The key is whether you can reinvest your winnings. If you can't, then shouldn't you just maximize expected value on each bet by wagering all your capital? - Dave Nolan