We always figure 6+45 to 7+00 flight time to our lowest reserves (good VFR, lots of nearby alternates, etc.), our group is good going down to 2,000 lb, but no less. I've heard of other crews going 7 hours+, but they've gotten pretty low on fuel. My balls aren't that big.
Good to know. We don't push our 300s that far that often...TEB-VNY-TEB however, we can do blindfolded.