  Using a recent census of flare stars from the Kepler survey, we have explored
how flare activity evolves across stellar main sequence lifetimes. We utilize a
sample of 347 stars with robust flare activity detections, and which have
rotation periods measured via starspot modulations in their Kepler light
curves. We consider three separate methods for quantifying flare activity from
optical light curves, and compare their utility for comparing flare activity
between stars of differing ages and luminosities. These metrics include: the
fractional luminosity emitted in flares, the specific rate of flares emitted at
a given energy, and a model for the entire flare frequency distribution. With
all three approaches we find that flare activity decreases for all low-mass
stars as they spin-down, and thus with age. Most striking is the evolution of
the flare occurrence frequency distributions, which show no significant change
in the power law slope with age. Since our sample is preferentially constructed
of younger, more active stars, our model over-predicts the super-flare rate
previously estimated for the Sun. Finally, we parameterize our best-fit model
of the flare frequency distribution for ease in predicting the rates of flares
and their associated impacts on planet habitability and detection.
