Alright kids....
Gearing will not change HP or torque, it will change thrust. Gearing is just like leverage. When I put my truck in 4LO, it still makes the same 220ft.lbs. as when it's in 2HI, but watch out, because nothing is going to stop those wheels from turning.
When considering the same exact engine, more revs = more wear, period. Whether that is relevant or not depends on a lot of things. For me it's not even remotely relevant, my bike will be totalled or sold long before the engine needs any real work.
Our stock tach is optomistic, just like our speedo. by how much? I'm not sure...but you all remember the 17.5K R6 redline snafu.
For practical purposes, MPG should only be measureably different when top gear is required. If a stock bike is running next to a -1/+2 bike, both at say 50MPH, maybe the stock bike is in 3rd and the modded bike is in 4th. If the stock bike runs through some twisties in 2nd, chances are the modded bike will run through in 3rd....with both bikes at or around the same RPM.