Per the LM34CA spec sheet, the long-term stability is +/-0.16C at T_max. Is the stability less than this value for temperatures less than T_max? What is the stability beyond 1000 hours? Does the sensor stabilize after 1000 hours or does it continue to drift increasing +/-0.16C every 1000 hours?
Regarding the LM285, its specified long term stability of the LM285 is stated as 20 ppm at 1000 hours. Is this ppm the voltage output of the device? Also, what is the stability beyond 1000 hours?