For cider, I check the gravity often. If it ferments too fast and gets too dry, I don't like to backsweeten. I'd rather rack the cider once a week and add gelatin before it quits fermenting then fermenting down to 0.992-0.994 (which is very very common) and backsweetening. Keep the natural sugars in there that way.
Check gravity as often as you want. Rack more often than you think you should. That's my mantra for great ciders.