2 questions on blood sacrifice

[1000yd_stare]

as i understand it, after the first turn, where you manually placed the blood slaves in his gem box, he will not sacrifice any more, UNLESS there is also a lab in the province.
If there is a lab, then the priest will, on his own initiative, get the same number of blood slaves as you had given him previously from the lab and sacrifice them. He will continue to do this until no slaves, or a change of orders.