A second possibility is that your husband is good at performing required tasks, but lacks the people skills that would make him a success. If that's the case, you can help him work on how he relates with others to succeed in an office environment. A third reason that people tend to change jobs is boredom. Perhaps your husband is so competent and smart, and the jobs he's taking are so routine, that he reaches a point where he can't take it anymore. Aptitude testing and vocational counseling can point a person toward more suitable work.
Some people actually enjoy frequent moves.
No matter what the cause, your husband's job-changing pattern has gone on long enough. Talk with him seriously about these four possibilities. Also, consider spending some time and money on aptitude testing and vocational counseling that could point him toward work that would suit his personality and skills. My husband was pleased since he'd gotten saved as a teenager, but I'm much more excited about growing in my faith than he is. In fact, now that I'm trying to teach our children Christian beliefs and values, my husband thinks I'm too fanatical.