we send our tammies off about 6-7 mths, about 85kg liveweight. we have also sent them off at 10 mths and older. meat has always been great, depends on your situation and how much u enjoy having them around. i personally like a carcuss to last us a good while so dont mind a bigger carcuss, as we have a big family. our first pigs went off quite late as we enjoyed having them so much. now we have a resident breeding herd its not an issue.
selling the finished pig seems easier at 85 kg cos people can buy half and not be swamped by stacks of meat, and u have the meat sooner.
hope that helps.