In reply to olddirtydoggy:
Hi- I'm the owner/designer at crux & Lightwave. The activated carbon is in a PU lamination - much more resilient than a conventional liquid PU-coating - and on the inside, so is not exposed to the elements (or UV) at all. There is no similarity at all to a DWR treatment in that respect. We introduced the fabric on the crux X1 tents 4 years ago, had several years trials prior to that, and is also currently undergoing some serious military testing - to date we haven't witnessed even the slightest degradation in the performance of the fabric. Basically, this should work as long as the flysheet lasts.