this has been discussed on other threads before. Here are some of the things that came up:
Those pudding cups do need to be refrigerated after they are opened, according to the manufacturers.
Here's what it says about the Country Kitchen fillings in the sleeves on their website. I've added the bold.
Pastry Filling-Bavarian Cream
Excellent for pies, pastries, cookies, tortes, and between cake layers. One sleeve pastry filling yields 3 cups. These pastry fillings do not soak into cakes. Refrigerate after opening; stays fresh for 3-6 months. Ingredients: : water, sugar, modified food starch, vegetable shortening (partially hydrogenated soybean and cottonseed oils), salt, artificial flavor, agar, titanium dioxide (for color), sorbic acid (preservative), and FD&C Yellow #5 & 6. Filled cakes may be frozen or refrigerated.
Maybe they just say that to avoid problems, but they really can be left out? I don't know since I haven't used them, but this is what the website says.
Do a forum search with the words filling and refrigerate and you'll get a lot of info. [/b]