I found committing to my 6th Kyu test really helped with my aikido overall, not just the techniques I practiced for the test. It really helped me focus my training; prior to committing to the test, I feel I was kind of drifting, learning little bits and pieces but never really bringing it together in to something cohesive.
That being said, some people may be able to bring it together without the focus of a test. If you're one of those people, great!