I took it twice in 2010, right after I graduated and moved (literally) to the other side of the world. I spent about two months basically only studying on the weekends. I maybe did a total of like two full PT. The definition of half-assing. I cancelled the first one (Oct '10) and, rather than buckling down and hitting the books hard, I continued with my half-assed studying for about another month and scored a 167 on the Dec test.
Hence why I went back for my third and final round this year. I actually did it right, this time. I started easing myself back into studying in February, but I really got serious in March. I followed a strict study schedule of about four logic games per day, plus at least one PT per week. In April, I'd gotten back into the groove enough to focus primarily on full PTs, so I pounded out between 2-4 of those per week until test time. All in all, I spent about four months doing every logic game from PT 19 onward plus about 20 PT in total.
Needless to say, I think this was more effective than the five-hour-per-week plan I tried before. I guess we'll know for sure in a couple of weeks.