Back to Basics - Definition of On Demand

I was reading today about the definition of "on demand" as it relates to the printing world. It seems about 60-70% of current print jobs are considered to be “on-demand”; requiring less than a standard turnaround (I believe that used to be called a Rush Job)...and an estimated 75% of short runs of 4-color work already average fewer than 2,500 pieces. I need a concensus of the numbers to "ratify" the definition...please.

Question one: What is the timeframe for "standard turnaround" time?
Question two: What is the turnaround timeframe to be considered "on demand"?
Question three: What is the average number of pieces in an order to be considered "on demand"?

Looking forward to hearing what you think!