I am currently running my Autos 24-7 all the way through flowering. They can handle it. So really. A dark period being unnecessary can be avoided entirely therefore avoiding any light leaks. Green told me he harvested 1Lb from a 70 day 24-7 Auto run. And since light is food for our beautiful auto girls, and they thrive in environments with light all day, there should be no need to turn the lights off. Even if you don't, a little light leak won't or shouldn't affect it much. However the rule of thumb is if your plants are in their dark period there should be zero light leaks whatsoever.
Side note. While running 24-7 lights. It eliminates the need for separate veg & flower areas. Plant new ones right next to to your flowering girls and keep growing 24-7. I'll be harvesting a half pound per month using this method, every 25 days I plant new seeds to keep the harvest times on schedule. Just something to be considered.
