I had to re-read the threat ( Wylde Ryde 1 , but it looks like 5 is the maximum number of level 3 thrones you can have.
I am good with whatever throne count we end up with. The thrones did not impact me greatly last game, Perhaps a few level 2 and a few level 3? That way people might be tempted to take a level 2 early. Which might be a good or a bad thing, heh heh heh…