I have an event on Friday, May 22 and I have to bake many cakes two days in advance. I am also planning to make cookies and decorate them.

For how long can NFSC (No Fail Sugar Cookies) stay fresh if I want to bake them much earlier?

I guess I can store them in airtight container for freshness but not sure when they will start getting stale.

I need your help as soon as possible.

idk but my girlfriend mailed me an nfsc in a business envelope -- wrapped in plastic but not bubble wrap just in plastic and mailed in a plain paper envelope -- she mailed out several to test it -- the cookie was still awesome -- she mailed from kentucky to me in memphis and i think she mailed to east coast and a couple other places around the country -- i was shocked that they did not crumble but they arrived tasty and fine -- they are quite sturdy -- 

if you can freeze them somewhere along the process that will buy some good time too -- freezing suspends it -- if you can decorate after thawing that would be best case scenario --

and thaw gradually -- watch for condensation

i would suggest you ramp up the vanilla or almond or whatever flavor you use though -- that would be the first to go/dissipate --

I have had un-iced NFSC cookies sit around for days but keep then tightly wrapped after they have been baked and cooled. They were stored at room temperature but not gotten into either.  I do use a lot of vanilla in mine and honestly believe they taste better when they have a chance to sit for a few days.  They do not seem to taste as good when they first come out of the oven for some reason. 

Dear -K8memphis thanks a lot, you have always helped me; and thanks to Happyfood too; both of your experiences have helped me.
Best regards

thank you, achee, and you are very welcome ♥

Just wanted to add, I find that if you are going to put them in cellophane bags, you also need to store them in a sealed bag or air-tight container. The cellophane bags, no matter how tightly you tie them, don' keep them fresh.