I suppose as a general rule if there is still visible fermentation to let it keep going. However even after the visual stops the gravity may still be too high - the only way for sure to know where you are at is to take a gravity reading. If you are really set against taking the reading I would at least until the visual activity stops.
From looking at the White Labs website I did see someone say the ale yeast does ferment like a lager which means extended fermentation times.
Good luck
