We were trying to avoid a double stroller.  We figured Cooper would be tired of riding in the stroller by the time that Nicholas got to heavy for a carrier.  Well, Cooper still loves to ride in the stroller and Nicholas is passing the 20lb. mark.  This means we broke down and splurged on a used double Bob stroller.  I have to admit that this makes loading the kids much quicker and going for walks much easier.  We all love it.