The answer depends on the surge protector itself. If it was an inexpensive model you should replace it immediately. It’s likely that the internal component which diverts excess electricity in a surge (called a metal oxide varistor) has already worn out from use. If you continue to use inexpensive models, make sure to replace them every two to three years going forward.

If you want to spend a little more and give your computer better protection, consider a higher-end surge protector with a light that will tell you whether you’re still protected. Another option is a series mode surge suppressor, which costs more but works by absorbing rather than diverting surges and lasts much longer than the metal oxide varistor type.