My NFSC come out of the oven fine, but after they sit awhile they are too soft and just fall apart. I have made this recipe hundreds of times and this has never happened before, PLEASE HELP!!!!!!!!!

add some flour to the remaining cookie dough

but did your oven go wonky on you? so of course you are baking long enough -- maybe the oven temp is off -- gotta thermometer in there?

When a tested/true recipe fails, one must check in your mind what you could have missed.  Are you *sure!* you measured right, added *every* ingredient, etc.   Many times it is our failure to do one or more of those things.   And as K8 said, check your oven. 

Yes oven temp is good. I did  have a lot of humidity in the air. In fact it had ruined the fondant on a cake and I had to redo it.  Would that have caused the cookies to become so soft that they broke apart?

Absolutely.  Sugar is hygroscopic--it attracts water--so left out, things with high sugar contents like fondant and these cookies will go soft quickly.

Thank you everyone!