When you buy inside a range, how do you know you are near the end rather than in the middle?

I never know, and you don't have to be certain. Do not seek certainty in trading. Even after a stock breaks out to all-time highs, you can't be certain it won't be a failed breakout and come back down. I focus on managing downside risk and finding the tightest entry point possible. The entry doesn't need to be very high; I need to be able to define my risk clearly.