Turbo SNG downswings...
 

You may be able to answer some of those questions by analyzing the graphs of those top players you mentioned. You should be able to pretty easily see how big their biggest swings have been.

Typically I've seen 30-40 downswing buy-ins in a few of the top players, but most of them have managed to keep it at 20-25 max. Though, I don't see alot of them having break-even stretches that last 1000 games.