Well Dec Silver and Sept Silver are almost identical. But my motive was also that Silver historically bottoms in July/Aug time frame and goes crazy in Sept and then falls sharply in Oct and runs back up into Dec/Jan/Feb. So to get past all the madness I post Dec as I prefer to watch Dec. And option traders have time for both moves up and down with the Dec contract without all the whiplash and running out of time trying to be too timely. The continuous contract I often post is the front month which I prefer to watch for chart patterns and clarity. So no other reason really. Long term charts need to be in continuous form for clarity.