The guy in this video claims to have gotten a perfect 180 and did so by redoing about 20 different practice tests repeatedly (there were only about that many PT's available when he was studying). http://www.youtube.com/watch?v=_sOsE0OlR00
@annakang1005: I scored a 179 in Dec and I'm now studying 11 hours a day to get a 180 in June. I'm Yale or bust. Ok I'll try and increase to 15 hours a day.