I believe say past 20-22 people kinda stop caring about the results of those tests. If you're smart you really need to start to put it to use, and it'll eventually show anyway, no matter what the results are.
Self-awareness? I would say it can be useful when you feel certain that you've reached your own maximum potential. Otherwise, it's either self-limiting (if you're aware of being average, or even "dumb") or uselessly self-aggrandizing.