Normally a question like this means you know you should drop down, but you dont want to because you're sure its just about to turn around. Just move down.

This limit should be set when you move up. In other words it should already be part of your BRM plan. For me, at micros I moved up at 20 and down at 15. No exceptions. At small stakes I move up at 30 and down at 25. Its personal, but once set it shouldnt change based on whim or feeling.