residence permit re -entry duration any limits?

i am a student and i have a residence permit issued by my university...since all my classes were done and i was just supposed to do some reasearch for the remaining year on my own..i headed to Sydney australia..i have been out of china since 8 months..i m doing my thesis so i just talk with my professor through email, nor is he interested to help me or ask me what i am upto.... i renewed my residence permit before leaving china and it is valid till 2013 september.....i m going back to china this march....would there be any issues regarding such a long exit i made from china????just worried..any information would be helpful...
thank you guys...