Long trips on back roads are what these cars are all about.
Unfortunately, unreliability when they're new and unsorted is what they're all about, too.
Most of us would love a five-hour trip on nice, back roads, but it's usually only after a few months of ownership that we're confident enough to try.
I think a good test drive would be an hour at steady, high speed on the highway. Go out 30 minutes, turn around, and return home. Surviving that with no hiccups would make me a lot more confident about doing a long drive away from civilization. Sustained, high speed stresses these cars where they're most vulnerable and will also show you how comfortable you'll be doing a long drive.
For the long road trip, could you have a friend or family member caravan with you in another car?