if they go way up, when does one get out?

I have a question for the people in here with long term experience in share trading.
If QPN SP goes way up as we all hope it does, when would be the right time to sell and take your profits and go?
Is there a sign that they are slowing or about to reach there peak?
Sorry if this seems a stupid question, but my experience in shares is 6 months long and I hold a significant amount of QPN shares in the hope of making some good profits in the near future.
I do not want to sell half way up the climb and find out I could have made a lot more money if I stayed or the other way and try to sell on a downward slide.
Any advice will be taken into consideration, thanks in advance.