How do I keep a bike feeling "new"? I think there is a subjective feeling of "newness" to a bike which is straight out of the box. What is it mechanically and aesthetically that creates that?  What can I do to prolong, preserve or restore this state?

N.b. I know of course that simply maintaining the bike goes a long way to doing this, but is there anything specific that can be done?
Aesthetically, it's just a case of keeping it clean. Use a toothbrush to clear accumulated dirt out of the little nooks and crannies, like the joints between tubes (especially around the bottom bracket). Waxing the frame can help keep that brand-new lustre.

The back of the chainring and spider, sprockets, rear hub, and dropouts, can get grotty pretty quickly, so use a gentle degreaser to keep on top of it. Same for the chain. Use a brush to get all the little bits of road dirt out of the links, then, with a clean brush, apply oil liberally. Brush it right in there. Wipe off any excess afterwards. As far as the feeling of mechanical "newness" goes, a clean, well-oiled drivetrain is the biggest contributor IMO.

Edit: Bike cleanliness pr0n