"When is it time to start thinking about another vehicle?"
When your wife starts to worry about breaking down in the current vehicle.
That's a pretty open definition, ain't it? A Toyota Camry with 250K on the clock would not worry me one bit (if I've been the one maintaining it) for a winter time cross country trip.
With cell phones, even a local break down at 11 pm is no biggie. Just run out with the truck and pull it home in a pinch.
