I know that on short commutes, they recommend changing more frequently (such as 4-mile work commutes). Life is often not fair or ideal, so it's nice to know what happens under adverse conditions.
This thread got me thinking I should enter that 30-mile commute from work crawing 2-3mph on an ice sheet at 25mpg. No telling what other vehicles got, but that's probably exceptional under the conditions.
It's kind of like last year when Curt Shilling pitched injured for the Red Sox and got them to a World Series championship - maybe not his best but done at a critical moment. Ironman triathalons are another one of those adverse circumstances on purpose (swim 2.4 miles, cycle 115 miles, run 26.2 miles in 18 hours
)
When people inquire about my Insight I give them a list of mpg under various circumstances - 40mpg under very aggressive driving (or very short commutes) - 80+mpg hypermiling at 50mph on the highway.