To answer your second question first (because it's the easier of the 2), Episcias do not go dormant. They are tropical plants and do not store needed nutrients in a tuber/scale. Once it's dead it's dead unfortunately. If you're having one dying back I'd check to make sure it's not getting below 55'F (12.7'C). To my knowledge this is the only thing that kills Episcias. Mine have been fairly tolerant of pests as long as they're enclosed in a high humidity dome.

Now about Sinningias, the answer is complex. If the Sinningia develops a tuber, it MAY go into dormancy. This holds true for many of the larger sinningias, however, it does not hold true for the minis and micros. If you notice the foliage getting very tired and worn-out looking, there's a good chance the tube is entering dormancy. Some sinningias will start putting up new growth when this happens, while others will want to take 1-3 months off from growing. If you have one that wants to take time off, I find removing it from it's pot, trimming away the roots, and lightly washing the tuber, then placing it in a ziplock bag with barely moistened peat moss, sealed, and then placed back in on the light stand (or window) works well. Some people have been known to leave them outside all winter, only to have them send up strong new growth and flowers in mid spring.

Thank you so much, this is really helpful information.