I generally get 5 colonies founded in the first 50-60 turns, build up my economy for the next 100 turns (and maybe build/capture another couple colonies), and then start pushing liberty bells around turns 150-170. My independence is normally declared between turns 170 and at the latest 200, depending on when I start the push. The WoI takes about 20-25 turns, but the last third is waiting for the REF to land the final wave so you can win the game. Maybe if your REF builds more ships it would be quicker.
Also, I don't rebel unless I have 1000 horses and at least 1500 muskets stocked up. So far, this strategy hasn't failed.