I've had my low fuel warning light pop on at only 66 miles, and usually it happens right around 72-75 miles. But those are times when we've been busting curves for all we're worth and accelerating to triple digits when possible in between curves. I recently mounted a 3gal AUX tank inside a tail bag on my back seat. It looks like SH!T FUGLY(IMO), but it sure takes the anxiety out of figuring where the next gas station might be, or not be. My wife has a 1.8gal AUX in a tail bag on hers.
There's a couple options out there for aftermarket larger fuel tanks that replace the OEM - adding over 2 gallons, but they both run well in excess of $1200 USD!!
Rob, a TX rider, has got an ECU flash from someone other than Tim Nash, (can't remember the company-might be UFO's version of pipe/ecu flash combo) that emphasizes lean & better fuel economy. Rob can go nearly 95 miles or so before his low warning light pops on. But I would have to say that Rob is one of the more 'conservative' of the TX hooligans that I've shared wind with. Tim Nash's flash is high on HP, but admittedly set up favoring the rich side, so as people don't go out and burn holes in pistons using his flash. Some people with the Nash flash go ahead and retain a PCV to have tuned locally so as to maximize the air/fuel mixture for their exact riding conditions and/or to lean out the a/f for better economy.