I am making a fall themed bridal shower cake for Saturday. I was going to make fondant leaves in fall colors. How far in advance can I make them? Would they do anything funky if I did them tonight? I don't plan on letting anyone eat them or anything.

You need to make them ahead of time and let them dry ... I'd make them as soon as possible... let them dry and then store in an air tight container

Thanks!! I'll do them tonight!

Fondant alone can be very suspeptible to the effects of humidity. If you knead in cornstarch, your fondant leaves will dry as hard as gumpaste. How much--hard to say, but as you knead it in you will notice it getting a bit stiffer. I just sprinkle some on my table and knead it in. If it gets too stiff, just knead in a bit of shortening.