I have an 8 month old making the trip, but I've set it up so we are only driving 3-4 hours max per day. She started to hate traveling, but things improved a lot when we got her out of the infant seat and into the larger child seat. Still rear facing though. She can see more and stretch out more, which I'm sure is a lot more comfortable.

1991 Mitsubishi Pajero XP TD LWB family hauler.