i was at the pittsburgh nass strongman in april and i saw a superheavy do 500 17 times and a dude 235 do it 13 times..the deadlift was the last event too..talk about impressive..i still talk about it..
I was told deadlifts for reps are a "real" bad idea too - so I've stopped. Been doing speed pulls for singles and with bands also. Going to incorporate some deadlifts for sets of ~ 8-10 back into the mix soon, but not for reps. All those reps could be pretty taxing on your CNS, so you may want to do them more infrequently than often.