Wow, these distances for driving in one day are mind-boggling to me, especially on vacation. My husband and I are leaving on a trip through the Smokey Mountains from Florida this Saturday and I've been tied up in knots for days trying to figure out if we can handle 480 miles on the last day. I'm off the opinion we can't so I'm thinking we'll spend the night somewhere.
That said, my one great regret on my trip to SA was that I didn't add the drive to Neu Bethesda to see the Owl House. And if you stay in Graaf-Reinet make a reservation to stay at the Andries-Stockenstrom Guest House so you can have dinner there. I've talked with a few people who raved about the food. But you have to make your reservations in advance since that's the only way you can have dinner there. Well--there's another excuse for me to return to SA.

Di - our distances are in kilometres - which makes them seem far longer than they really are.
On the last day one always tends to drive a greater distance - after all, what is the point of spending another night paying for a B&B or hotel if one is only a couple more hours' drive from one's own bed?

Rudi, Kilometres makes it seem shorter since I always know the miles are only about 60% of the stated number. There's the trade-off--cost versus comfort. 800 km (480 miles) seems like a long driving day to me. Although I recently did a round trip to Miami in one day and it works out to about that. So I can do it. I'm no wimp. :)