My workflow is as follows…
I make commercials for a regional TV station in Germany. We get our music and voice-over files from an audio studio in munich as .mp3s.
I load the mp3s into AE, and use them ONLY to time my animations. Then I render out as QT, without audio. I put the film and audio together in the Avid and make a master tape. No problems. Although, like I say, I never render audio in AE. But the mp3s sound fine when I make a audio preview or ram render, and of course played out of the avid.
best of luck
Simon