In my travels in the east, I have come across one dip as the grade changed significantly where it would have been close in the lower position. Out west, the chances are greater, but probably still not needed. More of a comfort thing where I don't have to actually worry about them hitting. And if you did go into a dip and they hit, then you would have to try and back out before being able to remove. In soft sand, that could be an issue.
It probably will be more of an issue with the being able to use the winch. I have never needed the winch for myself (knock knock on wood), but have used it numerous times pulling other folks out.