At a certain point in a SAGD operation, it is no longer economic to continue steam injection when the steam-oil ratio (SOR) becomes too high. A less energy intensive gas injection process following the SAGD process can prolong oil production by using the energy in place. Numerical studies of the injection of non-condensable gas, and a mixture of steam and non-condensable gas following a SAGD operation, were conducted using the CMG's STARS reservoir simulator. The simulation results suggest that, after three to five years of SAGD operation, when three quarters of the targeted reservoir is hot, it is appropriate to start a wind-down process. Injecting non-condensable gas results in a much lower production cost compared to continued steam injection; however, the oil production is reduced. Coinjection of steam with gas produces more oil than the gas-only injection process without substantially increasing the production cost. This is probably the desired wind-down process. Optimization is needed for the co-injection process. The choice of non-condensable gas depends on the cost and availability.