My guess is that each strain has a 'sweet spot' of proper light schedule and spectrum, but 18/6 during the growth phase is a good starting point. I much prefer using the 18/6 growth schedule, but there are times when 24/0 is a necessary evil.

Like if there is a problem with other lights being turned on and interupting the dark period, (bathroom light, kitchen light...) or if you can't afford a timer...24/0 is a good temporary option until you can rectify the situation.

Although the lights can provide overnight heat for the little darlings, it can be tricky keeping them hydrated properly, and they just don't perform as well under 24/0. At least not in my experience.

I'm not even positive that 24/0 is a good idea for autoflower strains, but I haven't grown any of those yet.
Rusty Trichome Reviewed by Rusty Trichome on . 24 hour lights Folks, I see lots of peoples using 24 hour veg times. All in good in some situations for a short period of time, but the plant needs some total darkness every day to work on root development. You will slow root proliferation by using 24 hour lighting, increase your electrical costs, increase the 'wear and tear' on the lighting system and needs rest daily too...... I think you will find that most of the experienced growers have learned there is no additional benefit from 24 hour Rating: 5