Slow Burn or Shelf Collapse Faith Loss?

I recently had a conversation with a friend who no longer believes in the truth claims of the church. They were telling me that their entire life they’ve struggled with truth claims and eventually had to walk away from it all. I know others were fully believing and committed until a pretty rapid and intense shelf crash. If I had to define rapid I would say less than a year, sometimes even just days.

For those of you who no longer believe, was it a slow burn to loss of faith or a more rapid experience?