F Visa Multiple Visit Conditions

I am to attend several conferences in the PRC over the coming months as part of my employment over there. I have been reading up on F type conditions and it seems that even on a "multiple entries over 6 months" F one I could only stay for 30 days at a time. My business requires me to stay in the country for a longer duration. What are the minimum conditions for re-entry. Can I fly to another country nearby and then re-enter on the same day? Do I need to fly back to my home country (Australia in this case) to then make the next entry valid? Can I extend the 30 days to say 60 days or even longer or is this no longer possible?