Hmm.. This is my #1 worry about these accounts... I'd hate to lose my playlist. Might be a good idea to save your playlist anytime you add/remove songs to keep them updated just in case.
This is the thing, you can link your facebook to only one account at a time, so if I want to link my facebook with my new account I have to remove it from the previous one that has expired. Will my playlists move with my facebook once I link it to the new account? I don't think so. I will try later on, but I doubt it.