What your plants do at night is uber important to their livelihood. They use the dark hours in your garden to eat the food they created while the grow lights were on. Plants also breathe in the dark.
Since night is shorter than day, its critical that you allow them sufficient time to create food and take in CO2, and then enough time to make use of their nutrients as well as expel oxygen. But that’s not the only reasons why ever grower should look at light timers as a necessity. There is this thing called the circadian cycle which according to the day length tells them what their task is at present. Short days and cooler temps is when they sprout and form the root system that will make everything you desire from your indoor garden possible. Longer days and higher temps tells them to get hot with the flowering and setting of fruit. They have a natural calendar programmed into their systems that gives them the knowledge of how long they have to ripen that fruit in order to create seed to sustain their race for the future.
This same inner clock also helps them to fight off pests and disease. Check out what they discovered in a study on plants and the circadian clock at Rice University in this video below.
So in essence, light timers that are appropriately set for the different stages of growth, are also part of your integrated pest management program. Take advantage of Nature’s rhythms and you’ll be fortifying your indoor garden’s defense against harmful intruders along with all the other reasons you need set hours for lights on and set hours for darkness.