swithing 24hr light to 18hr

I have about 5 plants and they are two weeks old. i was told to run the lights twenty four seven but now hearing that i should do 18 on 6 off. my question is, should i switch them to 18 on now or is it too late.

I don't think it matters being two weeks in...i'm a noob though so im not 100% sure.

You have a lot more leeway while in veg, to try out different lighting schedules. I wouldn't change it frequently, and definately not while in flower - but right now, you can change it without a problem. Personally I like the 20/4 - more growth than 18/6, better root system than 24/0. Whatever your preference is, will be fine.

I do 24/0 for the first week or 2 depending on growth then 18/6. One thing to consider is the start up of the bulbs as that requires the most energy in most cases and contributes the most to the life span of the bulbs. Say for instance if you done 18/6 as instead of 24/0 then after a week you've turned your light on 7 times, 2 weeks, 14 times, etc etc. All adds up.
I wudn't be too worried but dont keep changing

I've heard the dark period 18/6 gives yu is benefical though, but by how much i wouldn't know.

it really is personal prefference.. i was always one of the people who thought that plants needed some darlk period to perfom functions that they didn't or couldn't perform with the lights on.. but i just read an article a couple of weeks ago that told me that i was completely wrong about this, and mj will continue to grow and flourish under constant lighting, no need for a dark period at all..
the article was in i think cannabis culture and the dude said that plants grown under 24/7 will grow 33% faster than plants under 18/6... i grew under the 18/6
schedule too, but for any further grows, i will be using 24/7.
hope this helps some...
oh yeah.. of course this only works for vegetive growth and they obviously need to be switched to 12/12 for flowering....

I think it's all up to the grower, i know plenty of experienced growers who use both. I personally have used both. I like 18/6 because I feel that I should try to mimic their natural environment, but I don't know anywhere on Earth where there is light 24/7 other than a small area in the arctic where I don't think you'll find much weed growing due to the temp.
Also if your having heat issues 18/6 helps because it gives everything a chance to cool down, and the fluctuation of temps in my mind is a good and natural thing that aids with transpiration. It all comes down to grower preference.

plants are happier with 6 hours of darkness but either will work.Saves me on the electric bill...peace

Do whichever you want, just pick one and stick to it. Don't flip-flop back and forth between light schedules or you can stress your plant and cause hermies.

24/0 - For expedient growth of foliage.

18/6 - For medium paced foliage growth and robust root system.

12/12 - For flowering.

Less than 8 hours light can cause hermies.

18/6 cycle I think is the best.

thanks for all your help