Same here. 9 months, but I did not work at it regularly. But a lot of the time was spent posting questions on TRF and waiting for all the good answers to come in. Or needing to get to the HW store but can't go till the weekend, or stopping to build something smaller for another launch, or ....
Actually, I lie. That was my Formula 200 build. My Level 3 cert was on a MAC Performance kit that built in WAY less time. The documentation is the kicker for the L3 project, IMO.