Wyeast 1010 is a beast

I brewed an American Wheat on Monday and pitched Wyeast 1010 for the first time ever. Fermentation took off within 12 hours and has been bubbling along nicely ever since. Although I've kept the ferm temp between 64-68, this thing just keeps chugging along like an animal. I checked the primary this morning and krausen was peeking up through the top of the lid into the blowoff tube.

Anyone with experience know how long I should expect this to go? I was hoping to transfer to the keg next Saturday (so, a 12 day fermentation). Recipe had an OG of 1.042.

Last autumn, I ghetto fermented an alt on my deck in a bucket of water - the only way that I could get consistently cool temps. Anyway, the fermentation blew the airlock and bung off the deck - found it in the bushes. Luckily I was home when it happened, though the krausen was so vigourous I'm not sure that any beasts would have gotten in - at least in the short term.

I've used 1010 a few times and I think it makes a great American wheat beer. It seems to take its sweet ass time fermenting and even naturally carbonate, but YMMV. I brewed up a wheat last week and my LHBS was out of 1010 so I went with Kolsch yeast which 1010 is supposedly derived from.