I guess I must ride mine like I stole it all the time, because I most often average between 40-42 mpg. I am guessing that those who get 45+ don't ever get the RPM's above 4500, like niterider said.
IMHO though, I don't think it would be good to ride too long without ever winding it up a little bit. These bikes, as most motorcycles, were made to run at higher revs, and I couldn't imagine never getting above 4500 RPM's.
That being said, if you are getting 50mpg, more power (or less actually - haha) to you : ) I guess I do like to have a bit of 'fun' on mine, and for some strange reason, I feel that my bike compels me to rip it a little every now and then! Lol
Ride safe all.
7800 orig mi when purchased Jan 2011
Turned 11,000 mi Nov 2011
Taillight relocation kit
Chad's highway peg mounts
Otherwise, all stock
"But it's a dry heat - like the inside of an oven"