Shorthanded 3/6 Sample Size

Hey guys,

I know that technically one needs and insane amount of hands (like 50k or something) to get a good idea of what your BB/100 stat is like. However, after how many hands would you say you can get a good idea of whether you are beating the game or not?

I recently started playing shorthanded Limit games, I feel like I am playing fairly well, but my BB/100 is not showing that. At what point can I tell?