Both of mine got a lot worse in a hurry. The first one, the hard drive failed. Every time I restored it to fix it, I lost a little more storage. Eventually, when I took it in to the Apple store, they ran the disk check utility and it said the drive was bad so they replaced it.
The second one went, in a couple of days, from occasional skipping to the next track to skipping to the next track without playing anything. It would do this until the battery was dead. They didn't even bother doing a diagnostic on it, they just replaced it.
With both, the hard drive wouldn't stop spinning and the iPod would get real hot.