How long does a tank of medical oxygen last?

I found someone selling some oxygen bottles on craigslist. I only knew that there were more than one, that they're mostly full, and it comes with one regulator. They said to make an offer.

$30 and a 6 pack of homebrew later I came home with this:


There are 9 of the smaller bottles (C) and 2 of the tall ones(E). Every one is completely full, except two of the shorter ones.

I know this is obviously more than I need, so I plan on getting rid of some of them. However, I want to make sure that I won't run out for a long time because I won't be able to get these refilled, and I'm going to sell my bernzomatic oxygen tank style regulator (someone in my club has expressed interest).

I posted a similar thread many months ago because I, too, "acquired" a large tank.

A single large tank should last you 10+ years, IIRC.

They work? Do you just change out the heads and throw on a regulator?

Mine came with a dual regulator. Just put some vinyl tubing on the barb and turn the knobs....