In winter months we used to use an energy efficient bulb on a timer to provide light predawn and a bit post dusk adding up to 12 hours total daylight for them. It definitely increases laying. Basically we never saw a reduction in laying of our pullets over winter with that amount of light. This year I didn't bother setting up the lighting but likely will next year. We never add heat either and come January experience a few night lows of -30F.
The Original Poster is in Australia, it is not winter there anymore so the poster is correct to turn off the light--it's not going to help much anymore.