In the context of this thread, unless you can quantitatively describe a parabolic rise and have backtested a method of taking profits during periods of mania, then I would say to wait until the crossover has occurred prior to exiting. "The trend is your friend until the bend at the end".
The only thing that comes to mind is to have some kind of a formula which pinpoints a parabolic rise when it's happening, and then you switch to smaller time frame. Do you trade in a single time frame, or multiple?