Standard Deviation... Does anyone really know they're a winner?

[Dirk Gently]

After 31 139 hands and two months of playing one limit I'm up 449BB. If having 300BB at a certain limit is supposed to effectively eliminate your risk of ruin why does winning 449 BB @ 1.38 BB/100 produce a confidence interval that is still well into the negatives? My standard deviation is around 14BB/100 (6 max).

Is 300BB really not enough? It seems I'll have to play 100,000 hands before my confidence interval converges to even within 1/2 a BB of my poker tracker value. That's six months of very consistent play required to find out if a strategy is working or not... This game is insane, isn't it?