Now, If i make a big batch of icing and put it in my fridge to use when i need it so that i don't have ot make icing all of the time. How long will this last in my fridge? I would use it in like a week but I just wanted to know how long..
Thanks for any help!

It depends on the recipe. what the ingredients are.
For the most part shortening based b'creams can last in the frig about 2 weeks. For longer storage just freeze it in about 1 or 2 cup packages.