How many SNG's did you play to get +ROI

As a casual player 3-6 tourney's a night I finally rolled past the 500 SNG mark. I am not going to bother with ITM's in such a small sample but did wonder how long did it take you to get positive ROI and what was the most significant thing you did to increase to positive (ie book, coach, SNGPT). Did you start cold or have significant poker background. 99% of my SNG's have been at the 55 and 109 level. Can I assume an accelarated learning curve? I already know my weakness and it has been the hardest hurdle to climb and thats the bubble (what a surprise). I also assume this was the major hurdle for most others as well.