I was going to get into that earlier, but well, didn't.
Last contest, I tripled my performance on a rep event in 6 weeks. Deadlifted 400# axle for 5 reps at 6 weeks, and 15 in contest (though I missed 2 reps because of the down signal, like a chump). I think it's just a matter of time it takes to improve absolute strength in an advanced lifter vs strength endurance.
Big number you're throwing around Dave. Hell, I'm shooting for 600 DL and 500 BS @ 200 bodyweight as lifetime goals at the moment. Then again, these kind of numbers do seem to be common over at Marunde Muscle and p&b. Something to be motivated by.