There's no way to tell how long this process will take, but it's typically 3-5 years based on current backlog. If your appeal is denied by BVA, it can again be appealed to the Court of Veterans Appeals (COVA). This is typically the last station for your appeal.
Here are some of the highest paying jobs one can get with a psychology degree. Child psychiatrist - $189,301 average. A child psychiatrist can make close to a half million dollars in just one year.
So, the message is this: If what you care about most is a high-paying career, odds are, you should look at other college majors (although you can make a lot of money in psychology - check out the salaries of industrial-organizational psychologists, for example).