Why not? Set a non-repeating playlist of the length that you desire...

Admittedly, it's not as flexible as what you really want, for instance, it relies on you having playlists of suitable lengths, and you can't easily use it with a random shuffle of a large playlist. (You could by skipping _lots_ of tracks ). But it should kinda work.
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Mk2a 60GB Blue. Serial 030102962 sig.mp3: File Format not Valid.