How many hands before I know I'm a winning player?

[Banzai]

I just recently started playing LHE "seriously" online. I decided to buy Pokertracker and really chart my progress. I have a job, wife and 2 young kids so I only get to play short sessions a few times a week.

I mostly try and play 5/10 or 3/6 at WPEX but also sometimes at Pokerstars and I have a few dollars in Party where I will play if the games at WPEX are dry.

I choose to play at WPEX because it is believed by many to be the toughest site to play at and I want to be competing in the toughest games going to find out if I'm a winning player or not and how high I can play if I am.

So, how many hands do I need to play before I can establish with reasonable confidence I am a winning player?

Is it thousands, tens of thousands or hundreds of thousands?