Do the clocks degrade with time? I have wondered about this as well ...I have no particular knowledge regarding that question, but it wouldn't surprise me if such concerns arose as a result of flawed extrapolations from the fact that over time digital watches and clocks gain or lose time. "Flawed" for two reasons:
1)That would occur to some degree even if nothing at all in the watch or clock changes over time, just as a consequence of its initial inaccuracy.
2)If the master oscillator in such a device were to gain or lose the equivalent of say a minute per year, due to some combination of initial inaccuracy and changes in accuracy that may occur over time, that would amount over a period of 10 years to an error of less than 0.002%. In a digital audio device that would result in a corresponding change in pitch, which would seem unlikely to be perceivable even to those having perfect pitch. 0.002% would mean, for example, that a tone of 1000 Hz would be reproduced as 1000.02 Hz.
What might matter is significant degradation over time in the jitter performance of the device, but FWIW I am not aware of any credible evidence that would raise concern about that possibility.
Regards,
-- Al