Soukyuu, how long is a 'longer' in your opinion?
You keep saying that it takes 5 seconds to kill a monster, and that 1 minute is an exxageration. So what is your pefect time?
I say that because I've done levelling parties mostly in the 1~30 range and monsters certainly last a lot longer than 5 seconds.
That said, we usually do only have one or two thaumaturges.