I don't know if it's comparable, but Greater Manchester didn't call off the search for Keith Bennett for 45 years- and I would have to applaud them for their efforts. Many will remember he was the 12 year old child murdered by Ian Brady in 1964 and whose body, although very likely to be up there still on the Moors, has never been found. One can only begin to imagine the horror for these families. But, it's a big question, where do you stop? Sometimes, just one more day could yield the results they are looking for; other times you are just wasting resources- it's an almost impossible question to answer.