how far in advance can i decorate cookie for wedding favors. i know a sugar cookie recipe that i can make up to a month in advance and freeze the dough. but how long will the cookies last once they are decorated?

Not a cookie expert, but I think that depends on the kind of cookies you are making, and the icing.
I made peanut butter cookies (found here on CC) with RI over a month ago, and have just eaten the last. Holds fine if you store them in an airtight container.
Good luck.

You can freeze a decorated with royal icing sugar cookie-well wrapped for up to 3months. Thaw in container on counter. I personally wouldnt keep them that long esp for a paying customer, but that is the general guideline for frozen baked goods. I recently took some cookies out of the freezer from Easter and my kids ate them and they were good.

I use a basic cookie recipe (essentially the NFSC recipe) and a modified royal icing (Antonia74's). Without freezing, I try not to go more than 5-7 days from baking to consumption.

yup...me too....about 1 week from decorating and packaging.

I am making NFSC covered with MMF for a June 18 wedding. I am baking today and decorating the rest of the week. Then into the freezer they go. I have frozen this type of cookie many times, up to three weeks, and they are as good when they came out of the freezer as when they went in

thanks you all so much. these will be for my wedding and i will probable make tem around the middle of august and freeze them.
again thanks so much. i did not want to hav eto worry about cookies that final week before on top of everything else.

Once you unfreeze them, you have about 5 days. And then then they need to be eaten!