I didn't believe fully in the stuff from the age of 5 on up. I just joined (and tried to believe - then pretended to believe) because I got sick of the beatings - my resistance was worn down by my parents' violence and manipulation - and the 'guilting' and fear-mongering of the WTBTS.
Once I got away from parents and JW ex-husband, was earning my own lving - I was outta there! (I just wish I'd called my non-JW relatives - despite the fact my parents had isolated me from them - when I was 16 or so and requested a change of location... I would have saved another 14-15 years of my life from the WTBTS tyranny if I had done so - and succeeded...)
Zid