30+ buyins, mathematical explanation required

[Maulik]

earlier this evening, I was trying to explain to a friend why having 30 buyins is the widely accepted number for avoiding the phenomen known as 'risk of ruin' (at lower buyins). Kelly Criterion (google search) for more information. KC is especially useful for blackjack players enter Edward Thorp if you're curious.

Assuming a 3% edge in limit poker yields a requirement of 300 buyins at the lower limits. however, here I am not sure what is assumed for the corresponding variance.

I'll search the archieves tomorrow and post anything relevant.