I had to use DVDFab Express and DVD Decrypter on a couple stubborn discs, then I went back to just using Shrink with Nero 7. After that the last couple times it went through the Encoding process twice before finishing. It didn't do it before. Did I change a setting using the the other programs? Sure takes awhile now.
When you click on the Backup tab in DVD Shrink, go to Quality Settings. Be sure to untick the deep analysis option. If you leave this checked, it will analyize the disc in two passes to improve quality. Only use this option when compression is really low.
Typically if I have to go as low as 70%, I will use Deep Analysis and possibly the AEC controls. But experiment to see what the final quality is and what you're willing to accept.