I had a set of these for two weeks they started cracking, sent them back.
Nice looking and a good fit but I may have had a bad set, I use the shock Sox now.
How many miles? And yes, UV is a big factor on the cracking. I've used sun block on mine, but still get cracking after several months of use. I ride a lot and live in the desert. I've gone thru two pairs and just ordered some Shock Sox from the link above to try.