How frequently does the inspection and testing need to be carried out?

Table 4 that can be found in Australian Standard AS/NZS 3760:2010 recommends various retest timeframes which is dependent on locations and or environments in which the equipment resides in

Testing of items varies from: three monthly, six monthly, yearly, two yearly or five yearly testing intervals

If the workplace has a workshop or manufacturing area or is considered a hostile environment testing is generally carried out on a 6 monthly or yearly basis.

It's important your service provider has the expertise to competently advise the client about the retest time frames.