Need a bike to go further

[WHYNOWTHEN]

Oh internet sages, I need some advice from people with diverse motorcycle experience.

I currently own, and love, a 990 Adventure which I occasionally ride off the beaten path. During a recent trip to Baja, I was once again reminded how far away a gas station can be from a 990. Just a little over 75 miles. I started thinking about changing to a bike that allows me to get more lost without loading up on gas like a super-tanker.

What kind of MPG are you guys getting on all your fancy/not-so-fancy bikes?
I need something that can sometimes carry a passenger, do 80ish on the freeway, make it through long sand washes and up sections of lumpy singletrack, be capable of carrying a weeks worth of camping gear, have a range of about 300 miles, and make me smile too.

I appreciate your recommendations.