There was a point, number 7, which dealt with the idea that you must hold on to the 301′d domain in order for it to continue to pass authority. This is an important note because as soon as the domain expires you lose all of the authority that it was passing. I knew this, but I was not aware that Google recommends that you keep the domain for at least 180 days after the 301. I will have to agree with Stoney here and say that I suggest you keep it going for life! I believe that most people out there already knew or assumed this idea, but I am also sure that there are people that do not. The 301 redirect is a powerful tool of a professional SEO, but you must know all of the little nuances to take full advantage of it. And you have to do a lot of due diligence in finding and making the purchase of a good domain. I will get into that in our next SEO 301 class.