The theory (as I've read on other boards) is to shock the WAS out of the fog, and is typically done best in the early phases of the A.
It's a high-risk move, and it goes against the DB way. It is especially harmful if your W knows that it was you who exposed it.
In my situation, I was hoping the OMW would expose it early on (she knew about the A a month before I did), but she never did because she is 100% financially dependent on her H. Exposing the A would have risked her H losing his job (and ruining his career, along with my W's career).
M: 15 years BD: 6/25/14 EA/PA: starts 5/14/14 11/30/14 - A ends 5/15/15 - D is finalized. 11/28/15 - Start of new LTR with a wonderful woman (and still going strong)!