m0useanswered grow question 3 years ago Not to late, you can switch your light whenever you want with autos, most people do it week 4 or 5 or when its in flower from my experience.
Some growers do 24/0 for the first three-four weeks and then switch to 20/4 or 18/6. Sometimes down to 12/12 but I think that's unneeded.
I do 18/6 all grow as I use dry amendments, the soil microbes needs to breakdown first before the plants can benefit from it so its a bit slower.
There's a 55+ page form on this exact subject from auto-flower networks website, most people use 20/4 now according to their survey.
https://www.autoflower.net/forums/threads/whats-the-best-lighting-cycle-for-autos-24-0-20-4-or-18-6.3691/
However it is important to note it depends on the phenotype and strain your growing and also the type of feed your giving.
It's not good for the plant to be under 24/0 for it entire life, plants need rest, all living things need a downtime.
If you are using liquid nutrients and hydro setup 20/4 is good, or 24/0 for a short period of time is also ok during veg week 1-4.
The issue comes down to the plant up taking nutrients to keep the growing process going. Liquid = faster | dry = slower
Also hydro costs are an issue as well, yields don't seem to be crazy higher for 24/0 vs 20/4 compared to cost of hydro and plants yield and if I remember correctly some people on that form said 18/6 yields a bit lower in yield but quality of the bud is higher.
Best of luck