blair, like perry said if you feel they are light on stores give them the extra, if they are heavy now......wait.......keep hefting, when they start to heft on the light side add the fondant patties. also, like 40 acres said, it doesn't hurt to add the feed for extra security. i have done so myself and have this year.
i place shims on all my hives for winter months in the event i need to add feed. gives me the extra room to throw fondant/patties/ whatever in there and the bees seem to like the extra cluster space. my hives are pretty much heavy, but added the shims anyway. never know what the weather may bring. it's easy to lift the lid and quickly place something in to help them out.
a comment and suggestion; i would place any feed directly on top the frames, not on top the inner cover.......... an inner cover is a barrier to any feed placed on top of this.