Laoshi, you're quite right. I've worked for one employer for four years in Nanning. From the beginning I had students asking for more classes with me and I criticized my boss's girlfriend, the manager, for her unethical behaviors disclosing to the students how much I was paid and for her poor performance numerous times. In my first year, I refused to work when my employer rented me out elsewhere, but I was able to renew three more one-year contracts there. Had there not been one farce supervisor that my day to day work depended on, I would've probably signed another one year there. And, I could have. However, and ironically, this farce supervisor I could never get along with in 4 years wrote a fine letter for me, when I was leaving, as my employer was not up to the task.
Cheers and beers to all kinda letters our employers owe us