Chapter five in the EU GMP document entitled “Production” states, “Processes and procedures should undergo periodic critical re-validation to ensure that they remain capable of achieving the intended results.” Furthermore, Annex 15 of the same
GMP entitled “Qualification and Validation” states, “Facilities, systems, equipment, and processes should be periodically evaluated to verify that they are still operating in a valid manner,” although this requires only an evaluation of the validated status of a system. If this leads to unacceptable results, revalidation may be expected.
Periodic revalidation is also required by the World Health Organization (WHO) guidelines on GMP. Annex 4 of the WHO GMP document entitled Supplementary Guidelines on Good Manufacturing Practices: Validation states, “There should be periodic revalidation,
as well as revalidation after changes.” The fact that WHO is an international body (as opposed to a multinational one such as the EU or the Pharmaceutical Inspection Convention/Pharmaceutical Inspection Co-operation Scheme [PIC/S]) indicates
a degree of worldwide consensus especially outside the ICH countries.
You can also look ICH Q7A document.
When you identify that there is a potential risk on the product then you have to revalidate as per GMP.Since you are currently working on the Non-sterile process the risk is limited.
There should be an Event based Revalidation schedule like:
-Change in Regulation
-Change in product specification
I think its best to have a good preventive maitainence programme for your type application which reduces revalidation times, schedules and costs.
Time based Revalidation:
-As per GMP guidelines like EU/ICH/WHO
-As per number of working hours in a Day/week/year-- How much you use that praticular instrument and what are the wear and tear risks that effect the process.