A suitable system of maintenance is required by the legislation, your FRA should determine the frequency. The Government never intended the cash cow of every inspection being a full in depth check - this is detailed in the guidance to the Fire Safety (England) Regulations. Usually where the doorset has been established by specialist inspection to be fully compliant the wear & tear checks can follow the style of the FS(E)Checklist and can be done in house although some basic training is recommended. Professional checks would still be of use if there have been any alterations or changes, any issues found on the in house checks where 'seek professional advice' is the result and every few years as a backstop