The C24 CL is quite simply a magical set of wheels. As for aerodynamics, The C24 is among the more aero wheels out there, ESPECIALLY at its profile depth. I'm not sure if you've seen this, but note the very good score for the C24 in this test.
http://www.rouesartisanales.com/article-15505311.html
As for durability, Shimano doesn't set a weight limit and I have to agree. They have been VERY durable for me. I'd say the majority of the C24's aero benefit is likely from the low spoke count and the aero spokes, but it has amazing ride quality, great durability, rolls very smooth, and is proven to be quite aerodynamic.