slightly ot: DAT clock deviation

[Martin Czech]

Does anybody know about usuall DAT clock jitter and drift specs?
I mean the sampling frequency should be 48.00000 kHz, but
there will be offset, drift (temperature) and long term drift (aging).
I'm especially interested in short term drift (1s-100s).

I want to record the same thing severall times and add
the recordings up, in a matched manner. 

I could compensate for initial delay, but not for arbitrary drift.

m.c.