Thanks for those estimates on service life.
I'm a fan of not having surprises, so the further away from surprises I can be the better for my service uptime.
Just did a 1200 mile trip and once ran it down to 25 miles DTE, not a comfortable feeling since I had never been in that zone before with my E53. I quickly bought a couple gallons a few miles before my low cost planned fuel stop at Sam's Club in Joplin, MO. Felt a lot better
If I had a little gas can (with 1.5 gallons or so) in the vehicle at the time, I would have been less concerned.
Mike