Asphalt should be sealed first just after it has been initially paved and cured. After that, asphalt should be resealed every 2 to 3 years as regular preventative maintenance. Without regular sealing, asphalt will break down much more quickly.
Initially, small cracks are an aesthetic problem. However, when left untreated these cracks can expand and allow water to penetrate and damage the base of the asphalt. Like resealing, crack filling should be used a pretreatment and as regular maintenance for asphalt — every 2 to 3 years or sooner if cracks are large and/or numerous. Crack filling is one of the least expensive asphalt treatments and should be performed regularly. This blog post outlines the benefits of crack filling as a pretreatment.