as stotty and hewsan said, I do both ways I think. I tend to keep those images I like the most (who cares about the number of comments!) and those who display the kind of images I like to do the most - kind of my "style", if I have any. In the first cleanups I was deleting those images who had less comments, but then I gave up and started to delete those images that I did that were made more trying to following R's "standards" or "trends" in a specific period of time, but that I didn't like at all.