Well, we're near the 3,000 mile mark on the current trip, and we're still friendly.  We windshield farm, comment on nearly every truck/trailer we see, watch for interesting homes or farmsteads, determine the relative intelligence of other drivers depending on their driving abilities, or we just sit and watch the road go by.  Since I usually wear shades, I sneak the occasional catnap.  But after crossing the east half of AZ and all of NM today, there's not a lot of changing scenery to talk about.