There are a couple who leave and came back. But most who leave, will never see themselves returning to such a lifestyle again. Some are itchy about the pay differential if they are not getting enough outside, but still won't go back.

Big4 is ok when you are in it, and some people are apprehensive about leaving (future job prospects, work nature, pay). But once you exit, you will realize that there is a whole new world outside and what really matters