How often do the probe plates need replacing?

The probe plate is the only point of contact between the instrument and the test area, so maintaining it to its original standard is critical for accurate readings. It is recommended to replace a used probe plate with a new one if:
A) The probe plate’s underside shows more than one crease.
B) The probe plate’s underside exhibits more than a few dimples (raised or depressed spots).
C) The probe plate’s side profile is severely bent (note that a slightly and uniformly curved plate is acceptable).
D) Upon removal of the probe plate, the top side displays an impression of most of the spiral ridge from the underside.