I make the following buttercream recipe:

A.

Any advice from the bakers out there?!

I searched through the boards an found similar questions but not for the type of frosting I am using. Thoughts would be much appreciated!

Last week, while scouting out an alternate local source for edible printing, I spotted this page, on the web site of the very place that turned out to be my alternate supplier:
http://www.abccakes.com/Baking_Secrets_SGSL.html

Thanks for the link. That answers my filling question and is a good reference point. :)

I think their buttercream timing is a little vague given that there are so many different types of buttercream.
 

Yes, it is.

For my own part, since I use a simple cold-process BC (the recipe that's been on the back of the C&H powdered sugar box since before most of us were born, using all butter), I work on the basis that the shelf-life of ordinary, unopened table butter is weeks in the refrigerator, and months (or years) in the freezer, and that while opening the butter wrapper, softening the butter, and mixing it with other ingredients might introduce microbes, sugar itself is a preservative at the concentration found in frosting, and so the shelf life of the frosting is probably at least as long as that of the butter, under any given set of storage conditions.

And since I like my cake chilled anyway, I generally refrigerate my cakes.

And as to meringue BCs, well, I would imagine that using pasteurized eggs, and/or a recipe that involves enough heat to effectively pasteurize the finished frosting, would extend the shelf life.