You're making me drool on my keyboard.
I'm definitely going to have to make a cake this weekend.
This is what Wilton (from
http://www.wilton.com/cake/cakeprep/baking/quickneasy.cfm) says about cream cheese icing:
"Buttercream and cream cheese icings stored in airtight containers in the refrigerator keep up to 2 weeks. Use icings that have been cooked on the stove top immediately.
A decorated cake covered at room temperature will keep 2 to 3 days. Cakes frosted and filled with cream cheese icing, cooked icing, pudding or other perishable frosting and fillings must be refrigerated."
The only thing I don't like is that refrigerating cakes and icings changes the texture. I usually leave a cream cheese frosted cake out for the day we're first eating it then refrigerate the rest after we're done.