Peatland carbon may enter long-term storage in sedimentary basins preserved as either coal or lignite. To understand the process by which this happens requires extrapolation of our understanding of peatland carbon accumulation over timescales that greatly exceed those of Holocene peat. By applying this extrapolation, we deduce that the amount of time required to account for the carbon in 1 – 10 m thick coal seams must represent 105 to 106 years, an order of magnitude more than assumed in current interpretations of stratigraphic frameworks. Extrapolating peat growth to periods of 106 years requires consideration of the conditions of landscape, hydrology, accommodation space and crustal deformation required to ensure the sustained growth and accommodation of peat deposits. We conclude that the generation of accommodation space at low rates (0.1 to 0.2 mm/yr) can adequately accommodate thick peat accumulation over periods >105 yrs. However, generation of accommodation space at high rates (>1mm/yr) cannot accommodate significant peat accumulation. Key to this process is the maintenance of a saturated peat body above the level of clastic deposition. This long-term stability of the system has implications for our understanding of the processes that limit peatland growth under very low accommodation rates and the long-term validity of current peat growth models.