Well, according to the 300BB rule, you would stay there until your bankroll reduced to $60, which is 300BB at the limit below (.10/.20). I would suggest, though, that if your bankroll were to drop from $190 to $60 playing at the .15/.30 level, you would be looking at what was going wrong a long time before it got that far. In the (unlikely
) event that you were to lose 150BB, which would be only $45 (leaving your bankroll at $145), that would be the time to consider a drop back, or even a break while you check your playing style.
If you are playing according to the SHC, reading the articles, posting hands in the forum and learning from your mistakes, (you do make them, we all do), then you are unlikely to lose that much. It isn't out of the question to lose up to 100BB in a mini downswing, and it is strange how often that can coincide with a step up a level. I recently advanced from .25/.50 to .5/1, and in my first 1500 hands, lost 60BB. I wasn't making dreadful mistakes, just not getting my share of the right cards. I did wonder though, because it is natural to think that you are doing the wrong thing when you are losing 4BB/100 hands. Poker is funny like that, doing the right thing can cost you money in the short term. However, the next 4200 hands I have won 180BB (just over 4BB/100 hands), because I stayed consistent, and the cards went my way. So, play and learn, follow the guidelines, and it will work for you.
Cheers. And remember, when your pocket Aces get beaten by any old rubbish (it will happen), have a quick curse, and let it go. Pocket Aces won't always win, no matter what, so don't let it get you down.