dallinpackard wrote:So I had a 165 in June after studying since January and then after June only did drills but without taking a full length test and only on and off and somehow got a 172 in September. Do I need to write an addendum? And what would I even say? "I studied less and did better"
I think you would be fine doing one, but it also won't hurt you not to do one. I heard one of their admissions representatives say that they usually like to see an LSAT Addenda for score jumps that are above the average (which I think is something like 3-4 points), but I don't think its required. Seven points is a sizable jump (congratulations by the way, that is an awesome improvement), but it isn't such an astronomical leap that you should feel the need to explain yourself. If you do decide to write one, you can keep it to a few sentences that basically say something standard about how you focused on improving, and dedicated more time and effort to preparation. They don't need to know you studied less.
Tl;Dr: Really up to you, won't hurt you either way. Congratulations on a solid improvement.