Unfortunately, for mechanical devices with air seals, like pipettors, past history is no guarantee of present or future performance. IIRC, there was an ASTM? standard for performance and testing of air-displacement volumetric devices, but we used a Eppendorf document..
We used to perform checks on Eppendorf air-displacement pipettes and other brand syringe dispensers on a 1 month basis, with daily trend logging ( in Excel ) of area counts of a couple of selected standards used in the actual analyses being performed every day.
For the monthly testing, the acceptance limits for precision tests were those in the manufacturer's manual for the specific model ( inaccuracy and repeatability, IIRC ). In general, we found that many air-displacement pipettes failed, so we switched to gas-tight syringes with positive-displacement pipettes as plan B, still with monthly testing.
Our auditors were happy to accept those controls, but auditors are strange, and may impose their own rules. The only valid acceptance test is what a client's QA department accepts and pays for. I found that asking management for extra calibration staff, funded from the QA budget, helped to mitigate the number of "continual improvement" requests.
The rule is, if an error is found, how far back do you want to obtain a valid calibration result, and retest all subsequent data?.
