The answer to 'how long does silverfish treatment last' is that a typical silverfish treatment will last 3-6 months. Silverfish are difficult to fully eliminate, so regular treatment is often required to keep them under control. The treatment involves applying insecticides and sealing up entry points where they may be getting into the home.
Silverfish are hardy pests that can live for several years, so it's important to be diligent with treatment. The insecticides used in a professional treatment will kill the existing silverfish population, but new ones can quickly move in from cracks and crevices if the root causes are not addressed. Homeowners may need to have treatments reapplied every few months to maintain control.