The manufacturer does not give an expected lifespan beyond "Years". It mainly is determined on a visual inspection while doing the maintenance. As long as a soft lint-free cloth is used when wiping down the outside there shouldn't be any detrimental scratches to the outside. As for the inside the wipers should keep it clean, however the water quality plays a large role in this. If the inside of the sleeve is dirty and during cleaning you cannot remove the scaling or discover scratches, it should be replaced. In most instances the sleeve should last at least 3 to 5 years and if maintained properly could last well beyond that.