If you've read much of pianoblog.com or are one of my students, you know how important repetition is to me.
What many people don't understand about practice, is that the last 10 or so percent is where the majority of improvement occurs. Repeating a section 10 times vs. 5 times doesn't mean it will only be twice as good. In fact repetitions 8, 9, and 10 might add an extra 200 percent. (If you can't tell, I'm making these number up, but you get the point).
Its very similar to building muscle at the gym. The last repetition determines the majority of the muscle growth. How much should you repeat? There's an art to this. After a certain number you reach a point of diminishing returns, and you'd do better to work on a different section for a while and then come back. After a lot of practice, you'll get a sense of what is enough…there's a sort of "locking" in that occurs, where you can tell you actually learned something. As against a sense of murkiness and uncertainty about the section at hand.
But in general, I'd say most people err on the side of not enough repetitions. So, go forth and repeat.Want to learn piano but don't know where to start? I've taught hundreds of happy students! Click here for my free beginner lesson course.