"Snooping" -- what I prefer to call "intel" -- is sometimes a sad necessity. If any of us suspected our teenager had a drug problem, we wouldn't for a second hesitate to search their bedroom when they weren't home, to find out what we're dealing with and to proceed accordingly.
No, constant snooping once you already know what's going on, just for the drama and the titillation of it all, is not a good idea. But as the second half of Ronald Reagan's famous line about the Soviets -- "Trust, but verify" -- I believe it has an important tactical place in your arsenal when fighting to save a marriage dealing with an active affair.
I tell people to only gather as much as is needed, and that they can handle, emotionally. If they can stay detached, and use the information to help break up the affair and to better protect themselves and their family, it can have a strong benefit. If it makes them "go wobbly" and divert from their DB plan, then I discourage it.
