If I had planted a tree by my house every time a hiring manager complained that they had hired less qualified candidates after spending so much time and effort in the process, I’d be living in a forest right now.
The best candidates stay available for ten days at most. 60% candidates don’t complete time-taking application processes. And, more than 75% professionals who fit your idea of the perfect candidate are passive, i.e. not actively looking for a job right now.
More information: http://multirecruit.com/blog/you-are-recruiting-even-when-you-are-not-hiring/