Not sure that there is much 'evidence' to suggest the documented assessment times.
The whole process of documenting of vital signs only demonstrates that a set of vital signs (SOC, HR, BP, SpO2, Sed & Pain scores etc) was done. It will not demonstrate all the variations & detection / prevention of postoperative complications (patient/surgery/anaesthetic) that occur.
I would think that a process of 'continuous assessing & monitoring' may be more appropriate - given that some PAR units have electronic systems this might be an appropriate option.

However, 5 minutely for first 15 minutes then 10 minutely there after would certainly increase the patient assessment workloads for the PAR nurse - whould this help change the staffing requirements away from ANZCA to ACORN levels??