18 or 24?

I was told to keep my light on 24 hours a day during vegging, but then someone else told me that the plants wouldn’t use much more than 18 hours of light a day, so I would be wasting light and electricity. Could you clear this up for me?
Goddess loving the Goddess

The plants photosynthesize as long as the light is on. As long as the light is on, they are using it and continue to grow. Cannabis does not need a dark period during the vegetative growth cycle. Cutting the light period to 18 hours rather than letting it run continuously is just wasting time and space.

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