Our Data Team usually release an XML update twice a week so the list of patches requried by a machine even if filtered by OS could change from week to week before every patch Tuesday. If you want to keep the product list the same betweene each patch Tuesday without altering it I think it would be best to only manually tick off the patches that are required in the same.
Another alternative is to disable to automatic download of the XML. You would then need to download the XML file manually. This would keep the product list static for the your desired specified period. To switch this off go to Tools >>> Deselect Auto-Update Definitions. Also ensure to go to Tools >>> Options >>>> Definitions >>>> Ensure to Deslect Auto-update if it is ticked.