>The age of manufacture should not matter. A new camera is a >new camera.
Just because manufacturers tell you about firmware updates the do not tell you all of the hardware revisions they implement during the life of the product. Jest take a look at computer motherboards. There are many revision not just the BIOS but the hardware too by the time it ends its life cycle. That is happening because we are beta testers who report all of the bugs to the manufacturers and some things can be fixed in firmware and some have to be fixed in firmware. And some even require recalls. since cameras are not life threatening product you will not see as many recalls as cars but they do happen. One such recall happened with Nikon D1 or D1x (don't remember which)for a faulty capacitor (I think) that was responsible for denim pattern like banding at high ISO.
So, yes, newly manufactured camera should be better.