It was 1.30, before leviathan.I have the feeling that somehow self-governing is the only correct working colonial nation type, the other types are (from my feeling) slower in coring and aren't making any claims. Your long rebellion time could be related to this. The fast conquering is absolutely no problem, declare war on one and tick all his allies and his allies allies and when integrate all one by one in separate peace deals, the first wave of rebels was already during the war and was killed by my enemies.