Just the basic 750 mAh (quite discrete in hand), lasts me 5-6 hours, though I top them off (back on charger) around 4 hours in to extend the batt life. Told you, just a boring guy. That should have been my user name "BoringGuy".
So anyway, as we veer away from burning cartos, I think you said you topped off about 1/2 hour in. I read that folks top off at 50-25% left. I did not, therefore the burnt cartos. But really, if I'm using prefilled as I was, does the vendor expect me to toss the carto before it's done? So my conclusion is: most people using pre-filled are breathing in some burnt material. I'm sure some will disagree.