Dates on Advance Decisions

Someone who became slightly entangled with an e-mail discussion group of which I am part, sent this question to me and its other members {we are discussing EoLC, especially for patients in their own homes} (she is updating some guidance for the public, about Advance Decisions):

The MCA Code of Practice and various sources of guidance agree that written Advance Decisions to refuse life sustaining treatment should be reviewed by the individual 'regularly' in order to ensure their validity and applicability.
We advise our members and members of the public that if their health status changes or they have to go to hospital for an operation, serious treatment etc, they should review and re-sign their Advance Decision (having amended to reflect their change in circumstances if necessary). But for a person who is generally in good/moderate health, or even a person with poor but stable health, how frequently do you think it is necessary to review and re-sign their Advance Decision?

If anyone would be kind enough to answer her question, I will pass on the answers - it would help, if people would indicate their clinical role (district nurse, paramedic, etc).

A question I myself am interested in, is the following. If a clinician finds a patient in cardiac arrest, and is presented with an Advance Decision refusing resuscitation, assuming the ADRT 'looks correct' but it ISN'T mentioned in any patient notes, or on the Ambulance Service Database, do 'dating issues' affect the decision to attempt CPR. Should CPR be withheld, or only if certain dating criteria for the Advance Decision are met ?