Good question. I've watched 95% of the episodes between now and last September, when Season 3 started.
But I can't for the life of me, remember when, or if, I'm watching a repeat of an episode that has already aired.
How are you supposed to tell when the show has stopped airing new episodes?
The only thing I've noticed so far, is that the earliest Season 3 episodes had the lights over the audience dim down during every deal, whereas they stopped doing this for the later Season 3 episodes.