Dealing with job boards that keep resurfacing the same stale listings

My saved job search keeps showing listings that have been reposted for months. Some are genuinely renewed openings; others look like placeholders that never close. It's hard to know which deserve a careful application. I'm starting to check the employer's own careers page and record when I first saw each role. How do you separate fresh opportunities from stale board listings without spending all morning investigating every post?