Periodic searching software vulnerabilities is crucial.
You SHOULD check for vulnerabilities when:
Using or evaluating new software.
Improving existing software with third party components (etc. libraries, modules, plugins)
When a new CVE is out you are vulnerable. It does not matter if exploit code is already published on the Internet or not. Assume that Criminals are misusing the CVEs already.
A simple way to search for vulnerabilities is using
Search option that the US National Vulnerability Database (NVD) offers. The NVD is a product of the NIST (National Institute of Standards and Technology).
Simple Vulnerabilities Search
Keep it simple: Use the direct search option of the NVD database.