Let me see...
That tank is about 4 times the size of the little paintball tanks that I (and others) use and those are good for about 8 - 10 hours so it should be good for up to 40 hours or so of use.
If you're very careful about hitting the off switch on the regulator anytime you set the handpiece down for more than a few seconds you'll get longer life.
If you do a
lot of stippling you'll get shorter life.
But I'd
guess it should last around a week or so. Report back and let us know how long it actually lasts.