Question

how often should a probe thermometer be calibrated?
ideally, at least weekly
every time it is banged or dropped
before its first use
after long periods of time between uses
all of the above

Explanation:

Probe thermometers need calibration under multiple circumstances. Weekly calibration ensures ongoing accuracy. Banging or dropping can misalign internal components, so recalibration is necessary. First - use calibration guarantees initial correctness. Long - term disuse might affect accuracy, thus requiring calibration.

Answer:

All of the above.