In the lab we have been discussing backup policy and a colleague pointed out that a user might compile several times to review a trivial cosmetic change and cause a major change to drop of the end of the chain.
We could not see a perfect answer to this problem. Some primitive ideas..., 'keep the last file from yesterday' or 'do not count today's files when removing files'.
My network manager said 'Why not provide a courteous message warning to the user that 'Your backup directory is exceeding ten times the most recent source file size, please review contents of <Path>'
As I said... no perfect solution

Best regards,
RichardL