I use Tc exclusively and have DNA 75, 75C, and 250 mods. I always leave the resistance where they've been from the factory as I find ambient temperature plays a larger role than a few hundredths of internal resistance will. With that said, I record the resistance of a fresh build at room temperature and read it every morning to see what the mod is reading at the ambient temperature, in spite of the day to day temperature swings I usually find myself setting it back to the initial baseline setting. I have had fairly extensive experience with different builds and settings and I will say that I do lock my resistance always and rely on custom material profiles for the best results. One peculiar thing I noticed, something oftentimes overlooked, is the resistance changes from different ejuices. The resistance change is often enough to affect TC significantly for me. What kind of build/atomizer are you running?