Hi Axylrose, there might be a reason why you conduct the audit on a quarterly basis. The ISO 19011 Standard does not really specify the frequency of audit however, it clearly requires that Audit Planning and Scheduling must be based on risk analysis (ISO 19011:2011, Clause 5.3.5)
In our organization which is complex in nature, the frequency of audit for each department or section or function varies depending on the following considerations:
a. number of previous audit findings (internal and external) for said dept.
b. number of customer complaints
c. the number of employees and floor area of facility to be audited
d. the number of standards to be audited (example, combination of HACCP and QMS audit?)
There's always significance of conducting the audit quarterly compared to conducting it only ONCE a year. One significance is that you can early detect the gaps in your system and plan for corrective/preventive action to improve your processes.
However, you should also consider the availability of your auditors. As you may know that being an auditor, across any organization, is only an add-on task. It might be a burden to the auditor if conducting it 4 times a year, rather than twice. Not also to mention the resources needed during audit (example transportation, meals of auditor, accommodation and of course their time where they are excuse from their work).
Just a thought.