Concerning IR-1 visa, I would like to know the average time from NVC# to the consulate interview without using James shortcut and the average time using it. I mean, how much time can someone save using it?

The shortcuts and time saved only affect time at NVC. NVC to interview varies with the country. NVC in to NVC out varies by country also because you are mostly saving mail time. For instance, for China, one can reduce the time from 6 months to as little as two months. The "as little as two months" holds true with any country but how much longer it takes without the shortcuts can vary widely based on mail time from US to the benificiary's home country.