I have buttercream with cream cheese added into it in my fridge for 2.5 weeks. I am guessing it isn't useable anymore, but wanted more thoughts.....

Use the smell and taste tests If it smells o.k. it usually is. As I remember, Earlene Moor said *her recipe* was checked by her local health dept and can be kept UNrefrigerated for months - but she went through it much faster

Reminds me of George Carlin's "Ice Box Man" bit.
The refrigerator makes you feel good twice: When you put something in, it makes you feel really intelligent: "I'm saving food." Then, two months later, when it's got hair growing out of it, and you throw it away, it makes you feel really intelligent: "I'm saving my life."
. . .
"Smell it"
"It has no odor whatsoever."
"It's good! Put it back! Somebody's saving it! It'll turn up in something!"
"That's what frightens me: that somebody will consider it a challenge . . ."

I always freeze any left over b/c of any type. It will freeze for a long period of time. I keep check on it, throw out as i see fit. hth If you think yours is till ok, then , now freeze it, if you need it right now.

If it starts to grow hair and talk back to you...time to toss it

I've kept cream cheese in my fridge for 2.5 weeks and it was fine. The icing likely is also.