As someone who once had a long-distance relationship with a 400mi round trip, I'd say it's a little of both. There's a novelty factor, but there's also a part of it that some people find enjoyable.

Having the right car helps: trips made in my almost-busted Honda Civic were much less enjoyable than the ones in my brand-new-custom-ordered Mini Cooper. :) The right soundtrack, the right weather, and the right caffeine vehicle are major factors as well.