going from flower back to veg

I was wondering if taking 1-3 week old flowering plants back to veg using 18/6 light cycle is ok? I have heard to use 24 hr but I can't do that were I am living. Any help would be great!

i took a plant from my first harvest and put it back in veg.....it took a while for it to start growing again but now its taking off....i dont mine went back in under 24 hour but id imagine 18/6 would be ok it would just take a little longer to get normal again...wouldnt u think?