- as a gathering of evidence for a "cause" legal action of adultery, or to help you make a decision about custody;
- to confirm no-contact, as part of a MUTUALLY-AGREED-UPON transparency plan;
- you are concerned about dissipation of marital assets, or a drug, gambling or alcohol addition, or some other behavior that might prove harmful to the family.
If you can handle it, if you can detach yourself to such an extent that you are more "hovering above" the marriage than emotionally in the MIDDLE of it . . . almost like a "game-playing" mode . . . then the information you can gather is invaluable.
However, if it's only going to serve to beat you down, and defeat you, then it's probably best not to do it.