Upper panel: main sequence lifetimes as a function of the logarithm of the metallicity relative to solar, for models from 0.5 to 1.1 M_⊙ (bottom to top curves) as labeled on the right of the curves. The lifetimes are normalized for each stellar mass to its value at Z_init = 0.014. Lower panel: same as upper panel, but for selected models from 1.1 to 3.5 M_⊙ (top to bottom curves).