Without knowing what your tests do, that's hard to say. I know that we need to do some profiling on JSFUnit to see where the bottlenecks are.
A few things that might help:
1) Minimize the number of times you need to start the container. Ideally, you should only need to start it once for testing.
2) Minimize the time needed to start JBoss. There is lots of information on tuning if you look at the JBoss wiki.
3) Profile your application.
4) Only run the test you are currently working on. You can do this by passing the test class to Maven or Ant. -Dtest=com.foo.MyTest
I'll see if I can do some profiling of JSFUnit soon.