When repetition becomes boring then it is time for variation.

Variation is not innovation. Variation changes material which already exists, it does not involve a new idea, it involves tweaking something you already have into something different. The variation might be short and simple, changing the pitch of a note in a melody, or it might be long and complex, changing the dynamics of a complete piece of music. The result of variation is that existing material is transformed into something new and different.

Variation can be used as the sole tool for writing a complete piece of music, even very long pieces of music. The musical form known as theme and variation is a good example of this approach.