When should I replace the PAV parts as a maintenance?

Refer to the following mean time between failures (MTBF) as a typical reference value:
10V,20V,36V,60V,100V
200 W type: 78,778H
400 W type: 78,569H
600 W type: 72,221H
800 W type: 72,221H
160V,320V,650V
200 W type: 75,839H
400 W type: 75,667H
600 W type: 76,274H
800 W type: 76,274H
The lifetime of the consumable parts such as a fan depends on the usage, but it would typically be 3 to 5 years.