Just copied from EG7.pdf
Note: If you are including your police certificates with your application to the CIO, please ensure that your certificates were not issued more than three months earlier. Police certificates are generally valid for 12 months from the date they are issued. However, if a final decision is not made on your application before the expiry of your police certificate, the visa office may request that you provide a new one.
I submitted mine with all document to CIO, so PCC date a month or so before. So if they strictly apply the 12 month validity clause and my case not finalised within 12 months of PCC date then I "may" be asked for new one.
Regards