At some point there has to be some practical decisions made about rolling resistance. Once an optimal tire construction has been realized, rolling resistance will be pretty much determined by the that expendable rubber compound used on the outside of the tire. And there things are not much different than rollerblade wheels, motorcycle tires or car tires. A harder rubber compound will last longer and have less rolling resistance. It`ll also have increasingly poor braking and cornering performance as the hardness index increases.

Personally I`ll take better braking performance and cornering ability over a bit of reduced rolling resistance any day. As has been pointed out - at some point rider aerodynamics has more of an impact than tire rolling resistance anyway. At practical speeds - driving control over a variety of conditions and circumstances is a lot more important to me.

And those Schwalbe Marathon Supremes look really good - weight wise, protection wise and performance wise.