When Lightroom backs up the files and folders, each time it creates a new one. That is a lot of MB. Are you keeping the old files? Or can they be deleted?

I go in and clean my backups on occasion. When I do, I generally just keep the last couple. AND - I also keep backups of my backups on an EHD. Just in case.

Are we talking about the catalog backups or something else?

Yes, the catalog backups. Not the original pictures.

For the Lr backups, which in my case are stored in My DOcuments, I keep 2 iterations and back up 2-3 times a week my entire My Documents to an EHD, then sync that with my second system.

I use Synctoy to do this for the last year or so, and have had no problems and feel that having the catalog backed up to 3 seperate hard discs is secure enough.