What's the objective, flashing or continuous light? You should choose the operation mode according to this requirement.
In a first order, total LED intensity, as percepted by the human eye, will be proportional to the average current, or in other words the true battery load as long as no switch mode voltage conversion is involved. In other words, flashing a LED can't increase battery life. In an exact analysis, the LED efficiency slightly drops at higher currents.
Additional requirements apply for white LEDs that have to be operated in a certain current range to achieve the specified color temperature. Or, if flashing is the objective.
My computer has a print key to capture screens, by the way. You can copy screenshots to a *.jpg or *.gif file.