I've noticed a lot of the 'coming home' success stories tend to have had a checkered past of jumping from one belief system to another. We read about them swimming the Tiber, but I wonder how many move on to something else a few years down the road.
There was a thread a few years ago that showed that very fact. They simply switch again.
A lot of them become converts in the first place for marital "harmony" since many of them are marrying Catholics and figure it's easier to swim and risk drowning rather than try to convince their spouse of a more Scriptural perspective.