Abstract: An apparatus is disclosed for improving plunger seal life on a casing swab system. The apparatus includes a diameter adapter disposed between an upper end of a wellbore casing and a lubricator adapted to receive a plunger therein. The diameter adapter is configured to provide a substantially constant internal diameter between the lubricator and the upper end of the casing. A method is also disclosed which includes retaining a casing swab plunger in a lubricator adapted to receive it for at least an amount of time sufficient to enable entrapped gas and fluids substantially to escape from the plunger seal material.