1 1/2 to 2 years or so... as far as any observer was concerned, there was a bit of a slowing down followed by sudden cold turkey withdrawl from religious life, but that wasn't quite the full story...
For me there was some in vino veritas (With wine, we speak truth) involved for the first real crack to appear in my 3rd Gen JW thinking.
We were staying with the worldly inlaws for 2 weeks a few years ago. I took a shower whilst as pissed as a fart (drunk) after another great night out, and mused again that what the WT says about worldly people wasn't always completly true...
I nearly passed out when it hit me that it was just as well not everything they said was true*, becauase then it'd be even worse!!!! Eg: they were pushing the line that the congregations were a forgleam of the eternal prison paradise on earth and the screws elders were showing us the way life would be led forever under Stalinism God's arrangement... what a horrific thought!!!
I could only stay in 'the truth' if I ignored at least half of what the organisation said and did.
Understandably, this idea (that being a JW was bad whether it was the truth or not, and that it was worse if what they said was actually true) was the beggining of the end for me - but took another 18 months or so of H2O, Franz, Freeminds, College etc to come around to the natural conclusion of stopping being a JW in my own mind and stopping going along with it.
Once I couldn't stand it anymore, I got deleted as an MS as quickly as I could without causing too many problems for myself (like having to say why; I let then be relieved I was stepping down), went to one more meeting after the announcement and never, ever went again.
That's 4 or 5 years ago now.
Max
* 'Truth' in WT speak is about the same as 'Stable', 'Plug & Play' or 'Compatable' in Microsoft speak... nice sounding, but the meaning in the corporate dialect varies from the English language meaning of the word... (though W2k isn't too bad)