The time to re-varnish wooden furniture depends on several factors, such as the frequency of use and the environmental effects of the location of the furniture (e.g. sunlight, humidity). In general, if you notice that the polish has become dull or scratched, it's time to consider refinishing. Applying a new varnish not only improves the appearance of the furniture, but also protects the wood. If you don't feel comfortable doing the job, send a quote to find a specialist in your area.