I know I'm a bit late to the party but after 2 seasons on a Demo carbon I wish I'd gone with an alloy NS Stab instead. Not that the Demo isn't great to ride, it is, but I only went with it because it was cheaper than the NS at the time. If, you were Joe Racer chasing every 100th/sec and had a new frame coming at the end of the season then I'd definitely go with carbon but for a weekend of shuttle runs with the boys where your biggest goal is to not miss out on a beer after the ride then I'd stay with alloy.
The cost difference is a big point, longevity not so much as most of the damage done to my Demo, and I'm repairing the latest one tomorrow, is from it going in and our of utes, airlines, stone chips, or that dumbarse that knocked over my workstand while my bike was on it at Fujimi. It's designed to be strong when riding but it's the outside factors that I'm paranoid about which I wasn't with my old alloy bike.