Congrats on the new bike... I'm a relatively new 2015 Versys owner as well.
I was wondering what measure you used to determine mpg. I'm getting about 54 to 55mpg pretty consistently, using Fuelly (which I've always found to be very accurate). I ride it hard, and noticed it *does* like to be wound up with a sweet spot around 6000 rpms. Can't do much of that in 6th, with normal mixed riding... Below 3000 it starts showing signs of lugging. So, I'm surprised your mileage is that good riding in top gear most of the time.
I've noticed the same thing with the rear stock tire. Looked *very* scrubbed after the first few hundred miles, and after a couple thousand, looks like it'll give me 6000 miles on the top end. And, then I'll switch to Michelin PR4s (I got about 11,000 miles on the rear tire on a previous bike, and rode that equally hard).
Anyway, best of luck with the new ride. I've yet to really hear any new Versys owner voice major complaints -- on the contrary many (experienced -- including me) riders say it's one of the, if not *the*, best all-around bike they've owned)...
2015 Versys 650 Pearl White
[space holder for farkles...]