The 3gamma/2gamma ratio in uncapped, closed porosity mesoporous films (3.5-17.3% porosity) is measured from 50-400 K. For 10.4% porosity or less, the 3gamma/2gamma ratio for Ps annihilating inside the sample decreases slightly with decreasing temperature, while it increases for 17.3% porosity. We extract the temperature dependence of the mean lifetime from the 3gamma/2gamma ratio and compare to our calculations incorporating a model [1,2] of confined Ps. Estimating a reduction in the diffusion length of positrons/Ps with decreasing temperature, we find reasonable agreement for less than or equal to10.4% porosity, while our calculations disagree with results for 17.3% porosity.