i need to travel to China on business in January 2016. when do i need to apply for multiple visa?

i am not sure of the exact date as the machine we are going to inspect is still being commissioned but expected to be ready early January. I have visited PRC over 100 times in the last 20 years but sue to the holiday period in Australia and then in PRC i am not sure of the time i can get my new entry permit. Normally i would have renewed it but it was overlooked.Regards

Don Allen.