This misfeature causes me more heartburn than the others. I have to manually touch all of my build slaves once a month to keep them compiling.
Furthermore, you can't run unit tests without an interactive session, so the build slaves would have to auto-login on boot; we chose instead to not run the unit tests automatically on checkins.
You will need an internet connection to acquire a developer license once every thirty days but that takes about two minutes and that's about it.