We left the Mach-Zehnder and green mode cleaner locked and we found them still locked when we came back after about 2 hours.

The attached picure shows the transmitted power from the MC over a period of about 8 min (the longest that can be recorded with the oscilloscope) after two hours of lock.

The gain of the potentiometer of MZ was 9.9 and fluctuations seem to be of the order of 1.5%