I edit after I finish each chapter to catch any mistakes I may have made but I only just started going back to my original work to edit it. My reasoning for doing so wasn't out of laziness but because I was having bad writer's block and didn't want to fall out of practice while I wait for a sudden rise of inspiration. If done properly, editing can be just as productive as writing. Just in the past two weeks, I've added over 150 pages to my original work. Though I can see why many people would think that it is lazy.