Lukitoh,
We all understand what's critical here : The originals and backups should be stored in different places.
Your method of creating backups (from one to another PC and vv) in my view is a 'dangerous' one. Imagine what happens when an unknown (deadly)virus srikes one of the machines and is able to reach the other one through the network...... you could lose weeks of data in a few seconds !!

The best method :
Create a daily backup...e.g. incremental to tape/CD. On top of that a double weekly data-backup to CD/DVD and remove it from the systems (!). Store both discs on different locations...... Now you are able to 'roll back' to working situations....many weeks back... when needed.
It will cost a little money because you need 2 CD/DVD's every week, but it's nothing compared to the time it would cost to refind/redo the lost files.

Rewritables are NOT as reliable as normal discs.

Roel