I don't wait very long. You can right click the file and go to search and have it search for the exact file name. Sometimes it will pick up some sources that way.
If the file hasn't started to download just cancel it and try a fresh search. Vary your searches a little, search for the title, then search for the artist, or the name of the albumn, ect. The same principal applies to videos.
Another thing to try is to disconnect limewire from the network. In LW go to File>Disconnect, then have it reconnect. It will connect to different Ultrapeers and Leaves which may improve you chances of finding a good file.
Learn to use
Bitzi Web Lookup. It will help you sort out good files.
And another thread to see is:
Skills to continue downlds, Downld speeds, Searching, optimal performance.
Hope this helps
.