Hora, it depends almost entirely on the baby. We've done long journeys with ours, and as everyone says, as long as you take it at a relaxed pace, stop when the wee one needs to, it can be awonderful family experience. If you can, plan to stop every 2-3hrs unless babs is fast asleep, then you can get out as a fmaily and enjoy playing, walking, have snack under a tree by a river… all of these things can make the journey unstressful and a wonderful 'family only' experience.
However, it does depend on the kid.
My boy, now 4 1/2, is a dream. From 6 weeks old he travelled great, slept through the night (seruiously, 12hrs, still does always has) and was very transportable. We could drive anywhere and he was happy just being in the car (still is!). Did overnighters and then scooped him into a proper bed when we arrived, or long distances with breaks during the day.
However, our daughter (now 2)… let's just say that I am not looking forward to teenage years. Think we'll give her a ton of cash and tell her not to come back until she's married. she is still not great in the car, although better, but at 6 months we could do max 30mins then she would start screaming or vomitting or both. Hideous. She is of course, a complete daddies girl and has me wrapped around her little finger. Love them both to bits!
Kev