Worrying for no reason

I brewed my a english pale ale last friday my first attempt at my own recipe after I brewed it I pitched two packets of nottingham and let it set in my warm apartment for 12 hours or so untill I started seeing bubbles in my airlock I then moved it down to my cooler basement. After I did that I did not see much bubling and started to get worried but let it set for a few days today I went down there and the Krausen had fallen I was sure it was not done fermeneting so i pulled a sample to check the SG to see if I needed to pitch agian. My final SG was suppose to be 1.018 I measured it at 1.019 and it taste damn good. I am pretty happy with myself I just need to not worry so much next time. haha

Has it been anyones experiance that nottingham works really fast or is it just a factor of adding two packets of yeast?

Well, one packet is usually enough for five gallons of an average gravity wort. So, you certainly gave it PLENTY of yeast.