Thanks for all the great responses!

Another question that hit me (without getting into the whole aviation 02 vs
medical 02 vs welding 02 debate)

What is the average cost for your refills with aviation 02?

I really like the idea of Precise Flights pulse system, but I'd like to
compare the cost of 02 saved vs the cost of the adjustible pulse controller
vs the claimed increase in comfort over the regular non-pulse systems.

Thanks again, lots of great answers!

Jim