Well, I have a Zen Touch 20GB, which I would assume is exactly the same other than price and storage space.

On mine I am not sure if it really has 24 hours (I've never actually tested the exact power), but I usually only have to charge it once or twice a week and I use it quite a bit.

As for the line out, I've never really attempted this and I'm not sure if it has it. It does not have another jack for line out, but I would assume that you could use it to plug in from the headphone jack if you had the right cable.

Hope this helps!