The best applicants aren't lying in wait or filing hundreds of applications. They're happy where they're at, ignoring the dozen people a week who reach out trying to recruit them, until eventually they decide it's time for a change. Then they apply or get referrals to the handful of companies they find most interesting, and at least one is going to give them an offer.

So if you don't have a job opening posted on the day they're sending out applications, you may miss your shot to hire them.