Best option for the longest duration Visa - M type?

Hi I am an Australian Citizen planning on travelling to China in a few weeks. I have travelled and lived in China before - I have in the past got a 6 month M (Business) type in Hong Kong via an agency - I want to get a 1 year business type for China this time but I have read many different things online - I understand now that the business one has a 30/60/90 day stay per Entry. 90 being the maximum duration of stay.

My M type in 2012 was 6 months Multiple entry with 180 days stay. I am not sure of the current situation regarding the Business M type.

I want to get a 1 year M type with a 90 day stay per entry (or more if possible). I have had 2 tourist types and 1 business type in 2012-2013. The last time I was in China was in early January of 2014.

I have recieved an invitation from a Chinese company. What are the chances of being able to get a 1 year M type with 90 days stay or what is the best possible outcome for me? I would appreciate your help very much.