If my target is reached in a given trade, I will take off a sizable portion. Usually 50% of my position is liquidated. In the case of Six Flags, I took off a lot more. The rest I will let run as long as possible. I move up stops at my discretion.
As it pulls away to begin its next up leg, I will place my stops right below the last low. Once trends start, they can last a very long time. My goal is to catch as much as possible using house money. As a trend follower, I know I will never catch the very bottom or the very top. Catching 60% of a move is good enough for me.