Suspending a search is always a tough decision. One approach that is sometimes used is a matrix of factors to consider. The matrix doesn't make the choice for you, but does help to insure that all relevant factors are considered. Some of those factors include:

1. Survivability? - how likely is it that we can still make a live recovery?
2. Search area coverage? - what cumulative POD have we achieved for our search segments? How likely is it that we could have missed the subject in an area we searched?
3. Likelihood the subject is in the ROW (Rest of the World)? - is the subject even in our search area at all? Could this be a planned disappearance? An abduction?
4. Hazards? - how dangerous for searchers is it to continue?
5. Unresolved clues? - any clues we can follow up on? Have we found anything that would enable us to better focus the search?
6. Resource availability? - do we have enough searchers available to continue? You can burn through a lot of ground pounders in 7 days. Specialized assets such as trained dogs are usually in short supply.
7. Financial considerations? - a big one when air assets are being used. Agencies don't have infinite budgets for helo time.

It is easy to say "they should have kept at the search longer".
However, if you have searched the probable area thoroughly, and found not a single clue, what do you do then?
Search the same areas again and again?
Expand the search area to ever larger and less probable areas?
How many days can you ask volunteers to take off from work to keep searching?
What if you've already spent 3/4 of your helo budget for the year?
How long can you keep Park Rangers, Deputies, etc on the search and away from their other duties?

There are no easy answers.