For many years, the rule of thumb on brief-filing extensions was that you were pretty much guaranteed a 30-day extension and a 14-day extension.
I recently was granted a 30-day extension, and noticed the grant was marked "FINAL EXTENSION." I called the case manager to see if there was some mistake.
Apparently about a year ago, the Sixth Circuit decided cases were moving too slowly through the appeal process and told case managers to tighten up on extensions. The first 30-day extension would have the same standard as always, but any extension after that would not be guaranteed and would depend very much on the reasons given for the needed extension.