1 Computer, 2 Users and Accounts, 1 Apple TV

My wife and I have our own logins (each with our own iTunes accounts) on the same computer sharing a single set of music files.

2 Questions:
1. Is there a way I don't have to update both iTunes when I add new music?
2. If I sync my Apple TV with both accounts, will the device make two sets of all the music files? We both want to be able to access our playlists, but don't want duplicate songs on the Apple TV.

Any input would be appreciated.

Thanks
Mike