To be honest i have not tried, cooking a pizza was near impossible, keeping it at heat is very hard, its in my shed,unused for a few years now i gave up trying. i would not recommend this product at all. but this is just me.
I haven't tried it myself but would imagine you would have to keep topping up the fuel. The problem I found with the oven for pizza is that the oven is too hot when the fire is first going and then lack of insulation means it cools very quickly. I suspect this may be the case for cooking something over a long period too. This season we are going to try lighting a bigger fire, keeping it going for longer to build up a good amount of 'glowing embers' which may keep the temperature more stable for longer. Good luck