I have a lot of 5 star songs and because of this I also have quite a few smart playlists with '5 stars' as a limitation. But what about my 5 star songs that dont get a shout in these other lists? Simple. Using the great new playlist is/is not function, create a smart playlist as follows..
My rating is *****
Playlist is not (use all your 5 star list)
Limit To 1 hour (or your preference)
and select by least recently played (to keep it fresh)