Some people come to China and hate it! Most people come to China and love it. They signed a one-year teaching contract and find themselves signing again and again. I was no exception. However, there is a law in China which states that the maxiumum permitted length of stay in China is Five Years.
Now, you will read of people, teachers, who have been here longer. The 'law' states 5-years but of course, this being China not every provincial government strictly enforces it.
Hebei Province 河北省 does.
If you become sujected to the 5-year rule, the time that must elapse before that province will issue you with another visa (Z Visa) is 2 years.
I would be interested in finding out which other provinces in China adhere to the law. If you have any information that will help others, please drop me a line.

