How many days in advance can you make MMF? and Approximately how many recipes would I need to make for a 6"- which is 4" tall, a 9" - 4" tall, a 12" - 4" tall, and a 16" - 4" tall?

Its good for weeks upon weeks if sealed right...in an airtight container.... I would say that you will need 2-3 batches...

It depends on if you're making big or small batches. You can aways save extra for later. It's easer to make extra than to run out. When you get ready to use it just put it in the microwave for about 10 seconds and it will soften right up. If it's a large batch it may take a little bit longer.

I'm guessing it would take at least 4 batches to do all of those cakes..the 16" x 4 is a big cake!! Also, I don't know if you plan to decorate with the MMF but you would need to allow for that too! Don't worry about making "too" much, it will last a long time if wrapped in saran and then sealed in an airtight bag/container. Good luck and get busy!!