So it's quite obvious that adding a flux modifier makes your tool run off of power. But I'm not quite sure how the durability conversions are made. Does the tool keep track of what materials it's made of and subtract the exact amount of power needed (i.e. a 2400 durability pick will remain somewhere close to 2400) or will each block mined/mob hit subtract a predetermined amount of power (i.e. 1 block = 40RF).