depends on on where i am normally whenever i hit 1 bar on the gauge but if im in the sticks i start looking at 2 bars
200 - 250 depending on many variables, mostly if my back needs a stretch. When I did my long trips I was never far from fuel so I did not worry about that. It was all about the recuperating and getting back on the road.
As we all know, you are stuck in pretty much one position. With that in mind, fill-ups are more importantly thought of as a stretch and walk break. Early in the day I could ride further. Started looking for a gas station earlier and earlier as the day wore on.