According to the American Chemical Society Careers blog, it's good practice for scientists to periodically polish their résumés no matter their career status. After all, ACS says, "if you don’t keep track of your own professional accomplishments, who will? Keeping an up to date, comprehensive document will allow you to respond quickly to opportunities as they arise."
So, to keep a CV up-to-date, ACS suggests making a habit of adding new papers, presentations, continuing education, awards, and other significant accomplishments as they're published, earned, or completed.
"If you haven't completely overhauled your résumé within the last few years, it's probably due," ACS adds. "Does it still accurately reflect your professional self? Does it indicate where you are going? Should you consolidate older information, to make room for new?"
Finally, ACS says, editing is imperative. "No matter how many times you've read your resume, you're sure to miss something. Have someone else with good editing skills, read through it carefully to point out any errors or inconsistencies."