m0useanswered grow question a year ago From what I have read up on autos and light cycles some of the best results can be achieved with 18/6, there is a good form post about it on autoflower.net or something like it.
Some plants can tolerate 20/4 and few almost none like 24/0
The idea that more light = bigger growth is not wrong but nothing likes to be working 24/7 all living things need downtime and sleep.
This is why I never go longer then 18/6, I have seen plants mimic deficiencies when they don't get downtime and all the extra cost of electricity for the lights without that much bigger of a return on yield is just not worth it.
Also you really want to look into DLI, if its over 40 your giving the plant to much and its only stressing it.
You can provide a DLI of 40 in a 12/12 period with stronger lights or a DLI of 40 in a 18/6 with dimmed lights.
Example. my new Medic Grow lights will provide a DLI just a bit over 40 on 12/12 at 80% or 18/6 at 60%. At 100% no dimming on 12/12 they are giving a DLI of aorund 60. Overkill.
You can easily calculate DLI if your lights have an accurate PPFD map and your hanging them at the heights the map is referencing.
Best Of Luck!