Re: bankroll concepts - risk of ruin
If you are engaged in an activity that say gives you a certain win rate r and variance v per unit of time (or e.g. 100 hands), betting k times Kelly translates into having a bankroll of v/(kr). The attendant risk of ruin given k is exp(-2/k).
So if your v/r is 100 big bets, betting Kelly means having 100 big bets as a BR. Twice Kelly would be a BR of 50 units. You certainly want to readjust before getting below the 50 unit mark, and probably before going below the 100 unit mark.
You see, Kelly betting applies to a macro game, which averages over whatever goes on from hand to hand at the table. It is a continuous approximation which only depends on win rate and SD. There is a way to apply Kelly theory to micro decisions such as drawing and pot odds, and blackjack playing indices, but that is for another thread.
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