If you run your bike in 5th gear with rpms under 4,500...it's not unreasonable to expect gas mileage in the low 50s, with a 750 in good tune. Unless you're a "heavy" person, carrying a heavy load (or a passenger), fighting a good headwind, and/or you're riding in really hilly country.
Most people here seem to run closer to interstate speeds, and get average mileage in the mid to upper 40s.
The tank spec is 3.5 gals, so you should be able to go 150 miles or so, on a tank--if you keep your speeds down. I know because I've done it, repeatedly.
My bike is an '05 as well. For a "returning rookie" you made a damn fine choice for a bike.
The fuel gauge and the reserve portion of the tank though, will "tell" you to get gas before then, however (that is, the fuel gauge reading isn't the most accurate in the world, especially the lower half).
If you're still concerned, you might just do a good ride before your trip to your friend, and check it to see what you're currently getting.
Never heard (or read elsewhere here) of anyone out there that makes larger tanks for this bike.
Last edited by theauhawk; 06-09-2007 at 02:29 PM.