Shrink times also vary with the DVD. Slowest backup times occur with episodic TV show DVDs (cheers, star trek, sopranos etc.) that have +3 hours of video on each DVD. In those cases, even encoding only (without analyze and aec) might take 30 minutes.
On the other hand, if you do the time, you get more quality. DVDs copied with shrink are pretty much identical in image quality to the original, even if you're coding at 60% range.