What backup software do you use? I used to have a very good one on my last laptop, but I lost the disc and can't remember what it was called.
I just have a robocopy script set to run at 6am every day. It runs these commands that do it all. The /mir option mirrors the folders meaning you have to be careful if you accidentally delete anything and don't notice.
robocopy "f:\iTunes" "e:\iTunes" *.* /mir
robocopy "f:\iTunes" "\\home2\iTunes" *.* /mir
I suppose an alternative would be to stick another drive in and add another copy that only runs once a month to get a historical backup. Drives are so cheap these days that it's a false economy to try to save money on critical backups.
Edit: The first run of the backup takes forever as it's one hell of a lot of data but after that it's just incremental copies of new stuff and deleting old stuff. The benefit of this is that I have multiple copies of the data, if I go on holiday I just take the USB hard drive with me and I have my entire media library.