Early Finisher PPTS

Hi there!  I'm so excited to tell you a little bit about how I plan for those kiddos who always seem to finish before everyone else!  If I set aside 10 minutes to work on a problem set, some finished in 5, and some it took 15.  My timing was always off.  What TO DO? What TO DO?
 I knew that having relevant, engaging, materials for my early finishers needed to be a priority,  so I first tried rotation stations.  But, that didn't work for me.  I wanted to use this time to work in small groups, but my early finishers were needing me just as much.