How long will it take truffles to 'firm'?

I'm making this a href="http://www.cookthink.com/recipe/20439/Mocha_Truffles#" rel="nofollow"http://www.cookthink.com/recipe/20439/Mo…/a recipe. Well I made it around 6ish and I don't think they're quite firm yet but I've never made truffles so I don't really know what they should be like.