Funny you should mention this, as I was breaking in my new .72 over the weekend on a test stand. I used a 12x8 prop, 10oz tank, and 15% nitro w/18% oil content (mix of mostly synthetic but with castor). After putting five tanks through it (remember, only 4000rpm or less for the first 1-2 tanks), I then let it go full throttle for the sixth tank, still running on the rich side. It ran just a little under ten minutes. You have to remember, though, that you are not going to be running full throttle all of the time.

-Dave