My experience has been that beyond a certain age, (~50), people either begin to lose interest and become more apathetic, (and sometimes end up leaving), or become much more hardcore. I believe a lot of it has to do with missed opportunities, (or what is known as the "sunk cost" fallacy), where someone that spent their lives chasing a belief at great cost to themselves, begins to feel that they have no other choice than to stay the course. They will double down on their beliefs just as the problem gambler does when nearly broke.
As a bit of an anecdote, not long after a I left, I was speaking with a JW friend that you and I both know, (he of course was trying to convince me to come back). In speaking of his father, (who was well into his 70s at the time, and an ex-elder), my friend had asked him one day if he still believed. His answer was actually quite honest. His father said that "Since I had believed this long, and lived this life this long, what else can I do?". Deep down he recognized it was probably all for naught, however at 70+ years old, could not face that reality. Very sad, and very typical of those in this age group.
d4g