According to
LizzyM in the 2009 thread, deans list is seen as a major fluff, as most people applying are on it. If it is 100% based on GPA, don't bother listing it.
Also according to LizzyM and other peeps in last year's thread, it is misleading to adcoms to say you did something for three years, and then they see it was just a total of 9 months. If possible, it's best to put it separately. If you can't, maybe you can list one summer in the dates, and then say that you did it two other summers as well.
They'll read it.