Surprising improvement in gas mileage of my V-Strom motorcycle

Those interested in motorcycles or gas mileage might like to read the posting I just made on the StromTroopers forum:

After returning from our last summer road trip in September I noticed an apparently sudden and surprising increase in gas milage the first tank back. During the trip I pushed my 06 Wee the hardest ever--2 up with full side bags averaging 75 mph against a 10-15 mph head wind with peak passing speeds of 83.4 (GPS) [yes, VEE-guys, there were a few pucker moments when I really would have liked your extra 350 cc!]). Thought might have been filling fluke so decided to reevauate after 4 full tanks. Sure enough, a real increase in gas milage. Then decided to go back and check the first 4 tanks after summer touring the past 5 years to see if there was a trend. Thought this would be more consistent since all city riding (I ride year-round here in Seattle) while summer touring has significant variations in route, speed and headwind. I was stunned by what I found:
  
  
Every year, city driving gas mileage (averaged over 1,000 miles) consistently increased so that after 25k of riding it had gone up a remarkable 12%!

Nothing was changed with the engine and all the maintenance was done by the dealer (except some oil changes) on time according to the manual. I admit to not being an agressive rider--first set of tires lasted 16k miles. (BTW, when I purchased the bike I increased the drive sprocket 2 teeth to 17).

Does it really take this long to break in a Wee?