I got maybe 7 batches out of the 1.4oz bottle of O2 (that's the one you're talking about). I would run it for 30-60 seconds in each batch. Problem is, with the regulator you get with/for those bottles, you have almost no way to judge how much O2 you're getting. They're also notorious for going from barely any flow to full without warning (very small turn difference in the handle). I know, it happened to me more than a few times.
Keep in mind, the larger bottles/tanks of O2 are not all that large. About the same size as a 10# CO2 tank, if memory serves. You can store it with the regulator off of it, so that's not an issue. Just leave it standing up in the corner someplace, out of the way, and you'll be fine. Or put it where you store all your other brewing gear.
Since I've used both tank, and regulator, types, I can say (without hesitation) that the larger setup is by far the better of the two. You'll get far more batches out of even the smallest O2 tank that uses the standard regulator threads. You'll also get much better control over the flow rate, especially with the flow meter.
I would suggest looking around for the parts to get to the larger bottle/tank of O2 and regulator setup. Even if you order online, or from ebay, you should be able to get pretty much everything before next weekend. If you find a welding store in your neck of the woods, you'll be able to get a filled O2 tank there.