My husband is a SA. We have been in a successful R for almost three years now.
His past includes multiple PA with coworkers, strippers, prostitutes, and ultimately his brother's wife. The last betrayal with our sister-in-law (now ex!!) was what pushed him over the edge into recovery, first AA and then SAA. He has an amazing sponsor in both programs, has worked the steps, and sponsors other men. It is this level of activity, along with total transparency, full disclosure, and continuing work on with of our parts that allows us to stay married.
Not only have we stayed married, but our marriage has thrived despite the massive devastation his infidelity has caused in our lives and now the lives of our children, our two oldest just found out about his affair with our ex-sil.
We are proof that a marriage can come back from this but not with out a lot of work and a lot of willingness on both sides.
I hope this helps! Id be happy to any other questions that come up.