I just got my oven working properly. I had to make the orifice hole bigger than it supposed to be. Now it gets up to almost 600 degrees which is fine.
I haven't had it running long enough to see how much gas it is using, but, using science I'll take a stab at it.
The amount of gas you use with your oven depends on the BTU rating. My oven is small and it only burns 27,000 BTU's per hour as per the manufacturers label.
So.... If my understanding of BTU's is correct then we can figure this out for my oven. There are about 91,500 BTU's of energy in a gallon of propane. My oven only uses 27,000 BTU's per hour. so, 91,500/27,000 = 3.4 hours. According to this it will take my oven almost 3 1/2 hours to burn 1 gallon of propane. That is continuous burning.
Hope this helps.