I'm not 100% sure, but I always thought the AOD formed part of the Pre-Employment Medical and expired within the same 3month period. However, I know a few people who have done the medical but not the AOD test so I wonder if the 3months only begins upon completion of the AOD component as many of those that I know of did the medical (without AOD) at the end of June, which doesn't even get to a theoretical Oct GS 🤷♂️