The Visas in China can be a pain. Unfortunately China does not have any long visas for foreigners. My residence permit must be renewed every year but I wish we had 5 year permits or something.
I was curious as to how I could stay in China if I didn't have a job here. I could get a Tourist or Business Visa but have to exist every 30-90 days as you said and I think when you do that multiple times, the border patrol might cause you some problems.
Have you had any issues coming back into the country?
RE: What Is Chinese Business Visa and What Are The Rules?