But, let me try to give you a rough idea. Let's go with 2 batches of cookies because if you're going to take the time to make them, you might as well make more than one.
Cookies (two batches)....2 hours
Cookies (cool completely)...1 hour
Icing....45 minutes
Outlining....30 minutes
Flood icing (thin)....15 minutes
Flood Icing (rest)....10 minutes
Flood icing (fill)......45 minutesUsually, you'll have some sort of detail to add to the cookies. First, the filled cookies need to "rest" for an hour or so before the next step.
Rest....1 hour
Detail.....30 minutes
Then, let them dry overnight.
Dry.....overnight
***This does NOT include clean-up time!***
So, for about 2 dozen, simply decorated cookies, I would allow 5 hours of baking/decorating with 2 hours and 10 minutes plus overnight of inactive/rest time. (Did I add that right?) But, remember, it depends! :)
{In other words, don't start a cookie decorating project at 8pm the night before you need them.}
My advice....make the cookies a day ahead. Even two days. Even more than that and freeze them. Yes, they freeze...even fully decorated.
Another hint, royal icing can be made ahead of time, too. The icing will not be as stiff the next day, so if you have fine detail work to do, you may want to make it the same day. Otherwise, it's fine.
I love this post from my friend Gail of One Tough Cookie...here's a little nugget of wisdom from her blog: "No matter how much time you allow for decorating the cookies, allow more." See, she's smart and CRAZY TALENTED!
That's what works for me. Do you have any hints for timing your cookie decorating?