The authors review the latest fatigue and aging data on ferroelectric memory products and discuss thermal characteristics which limit the nonvolatile data retention storage temperature. They evaluate the effects of thermal excursions on the remanent polarization level in polycrystalline films. An excursion to an elevated temperature has been found to cause a reduction in retained polarization. The reduction is a function of the maximum temperature difference. The loss in capacitor polarization imposes constraints on the design of reliable integrated ferroelectric nonvolatile memory devices. >