i hit reserve while Adey and i were on the road last week. don't remember where we were, but we were on an interstate at SPEED, so to speak. the petcock was so stiff i couldn't turn it to reserve on the fly.
wound up having to make a quick move through pretty haeavy traffic, onto the shoulder, to rectify the situation.
i think we try to push the limit a lot(human nature i suppose.) i average around 134 before hitting reserve, but have gotten as much as 154 and as little as 120.
it's one thing to push the limit when you know your surroundings, but in unfamiliar locales i'd say between 100-120 miles on a tank is a safe bet.