I guess I am too cynical. In the cases I have been following in recents years (missing persons) silence from the police has not been a fair indicator of progress. Even knowing the police are working hard does not seem to guarantee any success in these cases. Missing person cases are unlike any other kind. I think LE is mostly silent and "secretive" by nature, perhaps even when it might serve them better to be more open.
I only say this after waiting and watching for up to four years on some other cases here where LE is mostly silent. They may still be investigating, but apparently have not made much progress. And since it is often the public who finds a missing person by chance, if they are found at all, maybe a new approach to these cases would be fruitful.
With LE searching and re-searching, interviewing and re-interviewing, that could be taken as still having nothing to move forward with, as much as being thorough.
JMO of course