FWIW, almost all of my smart playlists are "Limit to 25 songs" or "Limit to 1 hour", since that's about the longest uninterrupted listening I do. Worst case, you can back out of the playlist (choose "Menu"), then select it again to get a new set of songs.

This is not a bug. iTunes is literally interpreting your criteria. If you specify 25 songs selected at random (for example), then once a song is played, it conforms to your criteria and makes sure that you have 25 songs.

Maybe you have to turn off live updating. If that works and it stops after playing the initial 25 songs, then to get another set, select all the songs in the playlist and press Delete. This will refresh the list.

I suppose that I could turn off Live Updating, but I prefer to keep it on so that when I use the playlist on the iPod, it will refresh without having to resync with iTunes.

This still seems like a bug to me, because the iPod and iTunes differ in the way they handle the same playlist. The iPod plays through the playlist, advancing to the next track in the list until it reaches the end and then stops; but iTunes immediately adds a new track to the _bottom_ of the list (adding to the top would work better), without advancing to the next track. Hence it will keep playing until the smart playlist runs out of music that meet the criteria.

I just think that iTunes and the iPod should handle Smart Playlists the same way (and I wish they would!).

On my iPod (1st gen), the smartplaylists do not update on the iPod at all. This behavior is what I would expect.

Does this differ on the newer models?

I wrote an article regarding this behaviour on the iPod. The difference is confusing. I prefer the way the iPod handles it.

Caveat: If you select a playlist and leave the iPod alone and don't go back through any menus, then it will work its way through the list. If you go and have a look at something else, the already-played songs will disappear and more will enter at the bottom.

This, as I've started to tell people a lot, is something that should be reported to Apple