Even if we assume that you generate 1 billion hashes per second, it'll take you around 4,722,366,482,869 seconds to finally solve a block, given that the difficulty remains the same. That's 54,657,019 days. ![Tongue](https://bitcointalk.org/Smileys/default/tongue.gif)
![Tongue](https://bitcointalk.org/Smileys/default/tongue.gif)
That's just statistics though. You could wait for that many days and get nothing or you could indeed get lucky and get a block after 1 hour of mining at 333MH/s with a block eruptor.