If your Dura Ace wheels with worn out rims.
There is hope! until now there was no hope as replacement Shimano rims are hideously expensive. However the Kinlin XR31T is available in 16H and 20H drillings. This is a lower spoke count than I would normally suggest and I would not guarantee the build against spoke failure for the life of the rim but you can at least reuse your hubs.
For DA9000 C24 hubs (clincher) the lengths are 274mm front and 292/294mm rear.
Cost of this rebuild with black Sapim CX-ray spokes is £314+ shipping. Weight is 1600g but even though there is a weight gain these are better wheels than the orignal.