It was probably at the age of 10 or 11 for me. I had lived long enough to know the extent of the JW routine, and how nothing meaningful would ever change to allow some level of comfort or normality.
Having all the experience of my 10 or 11 years behind me, I would repeatedly try to extrapolate my future. What would my life be like? What would I make of myself? Would I ever be able to convince myself to buy into this crazy religion enough to believe that I was doing the right thing? Would I ever have ONE GODDAMNED MORSEL of FUN before I DIE?!
So, you can see my line of thinking, and how at such an early age, I just knew I would leave. Everything I saw around me led me to conclude that staying in would just result in a lifetime of bitter misery and regret. Fortunately, I never got baptised, and this allowed me to have the best possible relationship with family, given my non-participation in the religion.