Do I need more than one full image?

I have been using UrBackup to back up my family’s laptops and so far it is going great; except that I noticed that incremental images were taking up 30gb per laptop per week. Three laptops were amounting to 100gb per week for images which was a little storage hungry for me.

Two questions:

  1. Is this a normal amount of storage for an incremental image backup
  2. Is there any harm in stopping incremental images and just keeping exactly a min of 1 and a max of 1 full image backup? In that scenario does urbackup ensure it has the new image before it removes the old one?

Thanks for answers.