I'm pretty sure that's about what my bike runs at around 70mph. As far as gas mileage, I don't really think it's a big concern at only 5K rpm. I say "only" because our bikes don't even redline til much higher (can't remember what it is right offhand, but I'm thinking around 9K or so...?)
Keep in mind that a v-twin motorcycle can run at much higher revs than a typical v8 for example. And IMHO, these engines need to be run - like REALLY run - once in awhile to keep them at their peak performance. I have found in my experience that bogging these engines down by only running them around 4K rpm all the time causes carbon deposits to form and the cylinders to "gunk up" and actually decreases performance. So I wouldn't worry about the 5000 rpm. If you consider the fact that the normal idle for these machines is 1100 rpm, and compare that to the 4 or 500 most v8's are, that will give you an idea of what I am talking about.
Happy - and safe - riding!
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"