I started a robust porter a couple weeks ago with an OG of 1.07 using a smack pack of Wyeast 1056 American Ale yeast. I made a point of keeping the fermentation temp low (63-66) and fermentation kicked off quickly and has been going steadily. The bubbles through the airlock rate was very rapid early on, but slowly fell to about 1/92 seconds as of yesterday, and the krausen had gone from filling the carboy to a steady 3/8". I was concerned that the krausen hadn't fallen completely as I had seen in other beers I had made and I was advised to try heating the beer up to help the yeast finish fermentation. I applied a heating pad under my carboy and heated it up, over the course of 12 hours, from 66 to 70 degrees. The rate of bubbling in the airlock has almost tripled, from one bubble every 92 seconds, to 1 every 36 seconds. I am reluctant to go much warmer as I am afraid of off-flavors.
I don't want to hurry this beer, but I do need the carboy for my next batch. Any ideas how I should proceed from here?