I rolled over about one week early and I found out that the YM December contract has almost no volume (a few hundreds per day), a huge spread (20 ticks) and, worst of all, it is closed: http://www.cmegroup.com/trading/equity-index/us-index/e-mini-dow.html Cfr. attachment. I am not saying I didn't make a mistake by rolling over one week early. What I am wondering about is why there is such a wide spread (which is not the case with the other December contracts, both forex and stock index futures) and why it is closed. And, finally, I am wondering why there is such a difference between the September and December contracts: almost 100 ticks. I don't recall seeing any of these situations in the past few years.
I have news. The contract is tradable again, finally. It took them like 15 hours to get it back and working. Also, the 20-ticks spread is gone and now it's only 5 ticks. Finally. It was about time. Cfr. attachment. For the future, never roll over a week early.