You instead want to make sure the battery for your string of lights will last as long as possible. A battery will last longer if it powers a circuit with low current. How could you hook up a battery and 2 light bulbs so the least amount of current flows through the battery? Use the measurement tools in the simulation to check your design.
The resistance will be the greatest if you hook up the light bulb in series, and since resistance and current are inversely proportional, the current will be the least as well.
