I don't think most of them will ever go back.
I've talked with all of them on and off for years and they pretty much HATE the religion.
The only one's who've yo-yoed have been the one's who know it's the ticket to whatever they want out of other witlesses (aka Mommy, Daddy and family); whenever they need something, usually money, they "show an interest" get what they want and vanish faster than chocolate cake at fat camp.