How many times am I allowed to die?

[Arthur Morrigan]

I've heard you can't get a game over until the last emperor, but I'm unclear on whether there's a set amount of emperors leading up to him, or an infinite amount until a certain point in the game.

[Toph]

Literally infinite deaths until you take control of the Final Emperor.

Once you've defeated five of the seven heroes(this includes Kzinssie with Gerard), TYPICALLY you're next generation skip will begin as the Final Emperor.

[Null]

What Toph said, only the death of the final emperor ends in a game over, and even then having Coppelia in your party will give you a second shot at it. Even if you exhaust all the names it will loop back around.

There's no year limit either.