I don't know. They just believe that God will take them at the best time for them to go and they go with that. They do not risk their lives just to risk it but they are not overly cautious either. The story with the rock is not a typical one. But in that particular case that very old hermit decided that he was not meant to move and that it was a necessary reminder for him that the time was ticking and he was not to relax and treat each day like his last one.