Love the Nik collection. I still haven't fully explored everything it has to offer. In my exploration I've leaned toward the less is more theory. For example if your intent is to emulate an old photo, then think of how age would affect the whole image. You'd see fading overall, a dull slightly flat image. The sepia tone will turn darker with age. I'd also play with the grain sliders, and or explore the different film effects.