My take on the Marathon studs is that they are heavy and roll terribly. Despite having them pumped up to almost the max they are a pain to ride on bare pavement. I'd only ride them if completely necessary. I don't run non-studded Marathons, but compared to my second set of wheels outfitted with Conti Cityride tires I say that I'm a good 10% slower with the studs. With non-studs you don't have to worry about the metal spikes wearing through to the inside of the carcass, so in terms of lifespan I'd say you'd easily get 10,000 km.