I can't say you are wrong JB but I've known a few teachers who have stayed in China and worked unofficially elsewhere until their RP has expired, and have then gone on to exiting and re-entering the country with a fresh visa free of trouble. I suppose it all depends how broke or 'devil may care' you are after a Yuming experience. I mean some of us may consider it won't be a life-ruining experience to be forever banned from China and that a 5000 RMB maximum fine you'll have to pay. Supposing you spent all the money you had to get to Yuming from the USA, only to find after two weeks with them it was more than enough or you get sacked-What options do you have? Hitch-hike to the embassy in Beijing cap in hand maybe if you've nobody to send you cash from home. Leave China with a bitter taste in your mouth, tail between your legs. On the other hand you well may be able to get a nice little unofficial job for ten months and consider your eventual 5000 fine (perhaps a frog march to airport) and a ban from China just one of those little experiences that you'l be getting free beer on for the next twenty years.

If you do go to China make sure you get to know lots of other Westerners who can put you up in an emergency-(easy to make friends just go up and talk to people) is my advice in case you have to do a runner.