Adobe has dramatically changed how Previews work in Adobe After Effects CC 2015. In the sample video tutorial below, Total Training’s Brian Maffitt gives an overview of the new Preview behavior, and shows you where to adjust things to suit your liking.
Bonus: The Cthulhu maquette that Brian animated for this demo was created by Hollywood creature designer Lee Joyner, and there are additional effects provided by Rampant Design. Enjoy!
https://vimeo.com/user29079369/adobeaecc2015-advancedpreviews