How many hours on average was the 4 league round was? Pretty sure the final table would be way longer than that because of the blind structure and since its a grand finale with decent amount of prizes at stake, most players will be extra tight for sure.
Around 2.5 hrs. With 22 minutes blind and there was a final table in each tournament, obviously

I don't think this will last longer than that with 6 players but even if it does I am sure it will not be too much.
Those who survive 3 hours of play automatically go into "all in mode" every next hand at 3:01.

"Most players will be extra tight for sure", me too. No matter how long it takes and no matter how tight the players are at the beginning, I expect an interesting game and a good fight!