but would you consider this to be within the "normal" range of hybrid owner behavior?

Since you're close to the 40 mpg mark on the tank (assuming it's accurate) you have about 120 miles left after it hits empty. Just for caution I would want to be near a gas station around 90 miles. If I hadn't hit 40 by then I'd try it on the next tank.

Find a Mall parking lot at night and drive around in E Mode until you get to 40.