I hit the grunt call quite a bit in the late season. Every year beginning around the first of Dec. I hear deer grunting back and forth to each other so I join in. I've never actually called one in but I've carried on 'conversations' for about 10 minutes with the same deer.
It keeps me entertained between deer sightings. Not sure why they aren't that vocal before the rut though. I normally don't rattle either.