Not sure what you're asking. Medical results are always valid for one year - whether it's the initial exam or a re-do. I don't know what "they normally they process medical exams within 3 months" means - other than that they normally request and assess the medical results within the first few weeks/months after receiving the application at the visa office, and then they continue on with processing. If processing goes beyond the point where the initial medical exam expires, they will ask for another.