they do repeat, but mostly the ones you got wrong (to reenforce them for students using it to learn vocab). i have seen some repeats in different sessions, but not a whole lot....
and yeah, i\'m a big fan of this site. it satisfies my inner (and outer) word nerd, plus helps feed the poor win-win! i also have all of my tutoring and sat prep students on there once a day until they reach 2500 granis!
also, try celebrityenglish.com for grammar related celeb quotes. not as interactive and fun, but if you\'re into celebs, its got its pluses....