Elemental King/Queen summoning limits?

[Arryn]

I could have sworn this question's been asked and answered before, but I cannot find it: what happens if you try to summon a fourth Queen of Air, or third King of Fire, etc.? Or a closely-related subject, if you summon more than 6 (or however many there are) ice devils (or any of the other named critters in the game)?

{I've got this nice 28 air gem/turn income and I'd like to put the gems to a more efficient use than alchemizing them -- or Arrowing, Wind Riding, etc.}