I found the warranty to be the opposite: The new Motorcraft part had a one-year warranty, while the A1 Cardone remans from O'Reilly Auto Parts at least, came with a lifetime warranty. I have installed at least a dozen remans (a couple on my car) and have found them to last on average longer than the new pumps I have used. The longevity of the pump depends on who put it together, the pulley loads (belt tension) and abrasiveness of the coolant (DexCool is free of the silicates that can accelerate the wear of the seals). This applies to both new and remanufactured pumps. The lifetime warranty always helps.
(Sound of knocking on wood)