We routinely make 6-10 hour drives with both kiddos (DD is 4, DS is 6 months). Both kiddos have made the trip fairly routinely since birth (DD's first road trip was at 8 weeks, DS's was at 3 weeks).
I'd suggest the mirror, lots of talking to your babe, convertible carseat if they can do it (still rear facing, of course). I also found it helpful to bring lovey and paci for "naptime" as well as some small toys, rattles, teething rings, etc. for "playtime". When DD was small, I kept her lovey in my shirt when she wasn't using it so that when she did, she'd have fresh mommy smell.
Also, I'd suggest simply alloting extra time. We've found that a typical 5 hour drive takes us 6-7 and a typical 8 1/2 hour drive takes us 10. If you are willing to live with the stops and not get too worked up about it, things tend to go a lot smoother. We simply stop when the babes need to stop, hang out as long as they need to hang out, and drive when we can. For the most part this works well. I get high-strung on drives like this, but I have to remind myself to be zen about it all. . .
Good luck!