I've had metallics fade off a bit too, in a quilt that gets used just about daily and washed on a very regular basis. It doesn't look BAD, though - just not as glittery. Other quilts have metallics that still look new - so could be from lots of washing, could be from initial quality...either way it still looks good though.
They do feel a bit stiffer than regular fabrics but I've always treated them just like any other fabric and never had any ill effects.
I really like metallics - too pretty not to use them!