Another thing that has caught a few people out is that for international flights ICAO Annex 1 specifies that the medical is valid for 12 months from the date of issue (6 months from date of issue if you are over 60) and this frequently does not align with the expiry date shown on your CASA medical.
Example ; your CASA medical expires on June 30th, but for convenience you renew it on May 5th. Your new CASA medical certificate (assuming you are under 60) will show an expiry date of June 30th the next year. It will also show the date of your last medical as May 5th 20XX, so if you get ramp checked overseas on May 6th the following year, your medical will be deemed invalid. This has unfortunately caught a few people out.