Age can be a performance inhibiting factor in any device, including CDs.
Personally all other things aside, with CD players and digital in general, I would tend to go with more recent products (3-5 years old max) that many have been proven to enjoy. DIgital technology continues to evolve and improve, so there is a dividend there in general when you buy something newer rather than older.
The older device may still be in good condition and fine as well, but I would expect a large discount due to age and wear and tear accordingly and only buy if of particular interest for some reason. Sound quality would only be a good reason for me if say perhaps I had actually heard a particular older device years ago and still judge the sound quality to be a good value compared to other more recent competition. Retail prices alone are not a reliable indicator.
In general, I keep my digital devices that I like around as long as I can, often until they give it up in some way, or I see and hear something better that forces me to pull the trigger. The longer you wait to buy new with anything digital, the better off you will be again because the technology continues to improve at a rapid pace overall and older devices can become outdated quickly. That's not to say though that ones you already own and like are not good, just that things inevitably always move on sooner or later, especially with digital technology, where it is often sooner rather than later compared to many things.