When I lost my jacket and camera on a NWA flight a few months ago, I was told more than once that if it isn't found and returned within the first couple of weeks it is highly unlikely to be returned. Also lower value items are only held I believe I was told 45 days and after that there is a good chance it was either donated to charity or perhaps ended up here:

http://www.unclaimedbaggage.com/home.htm