From a fellow grower: I have 1 question about autoflower plants. Is 18 hrs on and 6 hrs off ok with LED on veg ok? Trying to conserve on electricity. Very expensive here.
Absolutely. Some even go 12/12 through the entire grow with autos.
All depends on your lights and if you are meeting the DLI range. There are ways to calculate what your DLI is based on the lights you have and what they provide in PPFD based on height above plants etc and then you can figure out how many hours of lighting is needed to reach optimum DLI (daily light integral) for best growth and yields. If ya wanna know more just ask or do a search for DLI on this forum or the web.
I just finished an auto grow and went 18/6 right up until the end, then I dropped down to 12/12. I was happy with the results.
Yeah what @Skydiver said, generally if you are using amazon led lights more is usually better ie 18/6 to stay on the safe side. If you are running hi spec lights you may be able to get by 12/12. Ask some folks here about the lights you are running and we can help better. Like @dbrn32 should be the go 2 guy!
I agree with trying to target ideal DLI.