Left: bolometric luminosity as a function of age for a 0.050 M_☉ brown dwarf as predicted by several different evolutionary models: Dusty (Chabrier et al. 2000) and Cond (Baraffe et al. 2003) models from the Lyon group; dusty (f_sed = 2), cloudless, and hybrid models from SM08; and models from Burrows et al. (1997). The range in model predicted luminosity is typically ≈0.2 dex (≈60%). Right: comparison of masses that would be derived from evolutionary models given (errorless) L_bol and age. Each plot shows the ratio of the masses derived from two evolutionary models, e.g., the top panel shows the Dusty model-derived masses divided by the Cond model-derived masses for the same L_bol and age. The impact of clouds on luminosity evolution can result in model-derived masses that differ by as much as ±25%, as in the case of the cloudy vs. SM08 hybrid models.