Hi Carole,
Glad you decided to post
I love doing S&H rotations. Love the tapes, the results, and the shortness of the rotations (usually 1 to 3 weeks for me).
You can do a rotation that includes Power Hour until you start to see/feel results, and can continue for as long as you want after that point. Personally, I can never do rotations for longer than 8 weeks, because I get bored too easily. Usually I do a rotation that uses specific tapes for no more than 4 weeks. However, I may do a strength rotation for 8 weeks, using PS for the first 4 weeks, S&H for 3, and then PS again for the last week. It really just depends on how I feel.
With Power Hour, or really any other endurance workout tape, I've found that my joints start to feel achy if I do it more than 2 times per week, and for more than 4 weeks at a time. This can kind of hinder my goals,though: If I want to increase my endurance, but have to quit before I start to see results due to joint fatigue, how will I ever build my endurance!? Hope you won't experience the same thing!
Anyway, I would also suggest that you determine exactly what your goals are when you start any new rotation, so that you can closely track those goals, and then decide if it's time to move on to a new rotation to mix things up, or if you need to stay with it for a bit longer.
Good luck!
Wendy