I don't know what the "rating" was but if you read my whole post you would have read that my race team was sponsored by Zipp and it was their engineer (not salesman) who told us which wheels to use. I don't think they would have put us on wheels that were going to fail. My race team, with eight tandems, has done three RAAMs (two for me) on them plus all the training and pre-race miles. All with only one failure which was mine when I hit a pothole at 50+mph. I destroyed a 30mm aluminum rim in a similar incident.

I also have a set of standard Zipp 404's on my single bike. They've been on there since 2006 including two RAAMs. These wheels aren't as fragile as a lot of people let on. I ride many more miles than your average cyclist in often much worse conditions.

Really the only reason they aren't usually daily riders is that they are expensive. They are no less reliable than any other wheel.