Thanks for the comments!
Yes, the timeout is there because the default timeout of 2 seconds (or so) is not enough since my iTunes is configured to copy the added file to the iTunes media library (1080p content often weighs in on a gigabyte or two). And if I googled properly "ignoring application responses" would make the add return immediately. However, I actually want it to block until the media has been added so that I can safely rm it afterwards. But please do correct me if I'm wrong. :-)