man, this thread reminds me how much easier the games used to be
it's really not, to be honest. 30k hands is
usually a decent sample for figuring out if you're likely a winning player or a losing player at a limit, but not something to accurately base your winrate off of. to get even close to knowing your winrate, i think you'd probably want 100k hands minimum, 200k would be much better though. since a lot of players move up in limits before they've even played that many, and since the games are constantly changing, having a grasp on your "true" bb/100 at any given time is pretty tough to do imo
a lot of great players have had 30k (and larger) breakeven stretches when it's clearly not indicative of their winrate
bottom line is you should always assume your bb/100, whatever it is, can be improved, that you can improve your game, but if you're steadily winning money over tens of thousands of hands that's pretty good