Does cream cheese frosting go off if left out? If no, how long can it be left out on cupcakes for? TIA

Depends on the cream cheese frosting recipe. (Some recipes are flavored with cream cheese and others are almost all cream cheese).

If in doubt, there's no harm in refrigerating the cupcakes. Bring to room temperature to serve (maximum out time 4 hrs.).

HTH

Thanks for your reply Jan.

I found this link regarding cream cheese frosting. Not sure what recipe you use however. http://www.earlenescakes.com/icings.htm