I know? I use the most modern version. He obviously doesn't have a backup in place right now though so just having one file that holds everything is never a good way to do it.
Until he gets a backup through a clone or TM, having all of his files condensed into the libraries with NO backups at all isn't smart. Copying them to the libraries then saving them off site is ALWAYS a better option.
Jesus; you wouldn't think people would be against the safest route.
Just to add on; I don't have stray picture files laying around because I have my main libraries on the drive, the whole system cloned on an external, AND the libraries backed up on a 2nd external drive.
Depending on the importance of his photos, he should have at least 2 backups of them. I'm sure as hell going to have 2 or more when they involve baby pictures and/or wedding photos.
Obviously having a proper backup strategy for irreplaceable files like pictures is important, but that doesn't have anything to do with the "duplication" of files the OP is doing in Aperture that I commented about.
Once the pictures are imported into Aperture, whether or not they are managed or referenced files, "duplicating" a picture just creates another preview image that you will then edit and create a set of adjustments for.
At no point does Aperture actually create a second copy of your master file. Unless you are editing multiple versions of a picture, duplicating the file is creating an unnecessary preview file and using unnecessary disk space.
The OP is using referenced files, so his file structure of master images needs to be manually backed up in some way. This can be through Time Machine, disk cloning, or manually copying the files to one or more backup disks.
Additionally, backing up the Aperture library will backup all of the versions and metadata that the OP has created within the program. The master files will
NOT be included in the backup because they are referenced. This backup can also be done through Time Machine or Aperture Vaults, as well as cloning or manually copying the library to an external.