Soil-bentonite (SB) slurry trench cutoff walls are widely used for subsurface containment of contaminants and groundwater control. In many cases, particularly for environmental containment applications, the walls are intended to serve as a permanent barrier with a life expectancy measured in decades. The compatibility of these barriers with the environment is considered during most design studies but a comprehensive review of the longevity of these walls is absent from the literature. This paper identifies key longevity issues, summarizes published literature to date and describes the current practice related to the longevity of soil-bentonite slurry trench cutoff walls. Principle issues potentially affecting long-term performance include compatibility between the backfill and the groundwater, impact of wetting/drying in the zone of the fluctuating water table, long-term property changes due to secondary compression of the backfill, potential for desiccation of the near-surface zone of the barrier wall and the potential for hydraulic fracturing due to the relatively low state of effective stress. The paper concludes with the authors’ summary opinions and suggestions for future research.