Dont do that...its cheating.
Although I won't disagree its cheeseness, and won't allow players to do such in my game (ok, so I can't stop them, but I will remember them and never let them in after that), it isn't considered "cheating" yet. Stardock (as far as I know) has not put out an official statement as to whether or not they intended it or not.
EDIT: I let 2 sets slide. Even I do that, but I am doing a legit upgrade. Nothing wrong with summoning your lesser priests when you are going to sell them and buy better ones, as long as you aren't going to keep repeating it, it's fine. Wouldn't be fair to someone who hasn't had their priests die yet and buys a new one, doing it completely legit. It's the people who end up summoning an army of 24 minions from idols and then get their talented armies of about 15 or so (Oak and Erebus) that really piss me off. 40 minions is and never was meant to be, I don't care how you look at it. It is just too powerful against single target DGs, which is most of em.
