Also, I wouldnt worry too much about end of tank scenarios. I have only ever read about it on the net- never actually met or spoke with anyone who experienced this. Besides unless your injecting inline i would assume most of the co2 rises to the surface and dissipates.
I have seen EOTD before...since I sell and test CO2 regulators more than most people
It is a real event, and can occur with single stage regulators.