I am wanting to make fondant flowers as accents on a cake. I am hoping to do as much work as possible a head of time. How far in advance can I make my flowers? Is there a "best practice" on storage? I want to try the marshmallow fondant - will this work well for sculpting?

I believe that you can make your flowers at any time...they last and will be available whenever you want to use them

In my experience, fondant and mmf flowers do not last more than a few days. Maybe others will say different, but I've tried several times storing the decorations in air tight containers, but they seem to not hold up very well; they get brittle. I've read that gumpaste works better when you are keeping them for a longer period of time. I haven't used it yet, but I added some in an order that I placed online, so I will soon find out how it does!