Shutter count matters, but it is not a simple pass/fail number. Different camera models have different shutter life ratings, and those ratings are statistical averages, not guarantees. A shutter can fail earlier or last much longer than its rated life.

So, 20,000 vs 5,000 actuations is only meaningful in context of the model’s expected shutter life. On a body rated for 100,000 actuations, both are relatively low. On an older model rated for 50,000, 20,000 represents more meaningful wear.

Actuation count is also a rough indicator of overall use, so it can suggest wear elsewhere on the camera, including the body, lens mount, and especially the battery. Just as important are how the camera was treated and the environment it was used in.

A failing shutter often shows problems first at high shutter speeds, such as partial black frames.

Bottom line: use shutter count as one factor, not the only factor. Check the specific model’s shutter rating, inspect overall condition, and consider signs of heavy use or poor care. A well-kept camera with higher actuations may be a better buy than a neglected one with a low count.