Yes, this is a real difficult risk for people to admit to themselves. My wife is in charge of watching me when I drive and to not believe me when I look tired.
We make many stops... at least 15 minutes every 2-3 hours and a half hour to an hour every 6 hours for a meal.
We always have snacks, drinks and candy for the long drives too. And driver gets to pick music to avoid sleep inducing ballads.
Really important to stop and switch drivers any time it is needed or to take a break and a walk!