In my opinion, 24 hours is way too long and totally unnatural. Cannabis can only grow so much during any 24 hour period and this tops out at about 18 hours. Any longer and you are basically wasting electricity, as the return in growth versus electricity used is almost zero. Plants do actually need to "sleep" and undertake certain metabolic processes during the dark cycle and giving them 24 hours of light will deprive them of this need. Have you never seen your plants last thing at night, then when checking them in the morning gone "wow" at the change in their appearance? This is why they need "sleep" time. Why also do you think 18 hours has become the "mantra" of the cannabis growing business, it was not decided upon for no reason, it was chosen as it is the best answer for optimum growth. I like to think of the 6 hours of dark as; 2 hours to rest, 2 hours to repair and 2 hours to get ready for the new day ahead, and this is basically the 3 things plants do during their "sleep" time. Being greedy and pushing your plants like machines at maximum velocity is both unkind and unnatural. In the end, something will break and all of your time, money and effort will be for nought. Your plants are living organic beings that should be treated with kindness, love and respect. They are not robots programmed to produce bulk "product". If you want flowers to be proud of, produced by happy and healthy plants, an unnatural thrashing with 24 hours of light does not have a part in that process. They are your babies and should be cherished, not over tired, exhausted, stressed out bud making machines. Stressing them with 24 hours of light could also lead to other problems, such as hermaphroditism, due to the totally unnatural light cycle inducing stress related issues to arise. It is up to you to choose what you do, but from my experience and knowledge, giving them 24 hours of light is problematic on many levels and is usually driven by greed from people who do not understand basic plant biology or care 100% about their plants' wellbeing. Enough said. I will now crawl back under my rock!
Hope this helps,....
Organoman.