If you find top talent keeps slipping through your fingers, you might need to step back and reevaluate your hiring process. One way to review the interview process to make it a better experience for candidates is by actually talking to past recruits that turned you down.
Ochstein recommends reaching out to candidates who didn't take an offer by assuring them you aren't trying to hire them again, but just that you want to talk about their experience. If they agree, ask them what the company could have done differently and for their honest opinion about the interview. By figuring out what made them choose another company over yours can shed some light on what needs to change in the process, if anything. It's also a great way to get an objective view, since that person is less likely to worry about saying something nice simply because you're their employer.
If you can't get any past candidates to talk to you, go internal. You can always ask the people who currently work for the company what they did and didn't like about the interview process. They might not be as honest as someone who doesn't work for you, but hopefully they can give some helpful feedback. Alternatively, if you have recruiters, says Ochstein, you can even get them involved or hire a consultant to evaluate the process.