I've got Schwalbe Stelvios on my Dahon, too -- although they're pretty low mileage since I just got them in May. Out of curiosity, where are your Stelvios shredding? The part where the tire touches the road, or where the different compounds meet (my tires are two colors, and I think it's because the material is slightly different in those parts of the tires)? Are they just particularly vulnerable to road debris, or is there something about the construction that isn't holding up? Just want to know what I can expect in terms of wear and tear.

I hear good things about the Schwalbe Marathon line -- a slightly wider tire than the Stelvio, but maybe a good idea when PNW's rainy season comes around.