Just to be clear, backups that store multiple versions of files aren't a bad thing - they're actually a good thing. They give you more options for restoring files and often let you recover a good version even if your file got screwed up somehow and you didn't notice it for a while.
You shouldn't have to worry about running out of disk space, as most backup programs that keep multiple file versions will automatically start deleting the oldest versions when the disk fills up. So as long as your backup disk is at least as large as the disk it's backing up you'll always have a backup of everything. Any extra space will be put to productive use holding older versions of files.
The only sense in which this is a problem is if you want to use the extra space to store something other than backups - but strategically speaking it's not a good idea to mix backups and non-backup data on the same drive anyway.