Babysitting seedlings that were started too early for your zone like tomatoes is a pain.
If you don't have them under lights at the proper distance, you are additionally going to get long spindly weak seedlings. Not the best thing.
Shorter stout plants with thick stems, tighter internodes, and fibrous white roots are what you want.
Also Thigmomorphogenesis, the effect of mechanical stress on plants, is important to know. In nature, wind is the mechanical stress that triggers a hormonal response in the plant that causes the seedling to form shorter, sturdier stems, thicker leaves, reduced height and more robust root systems to anchor themselves You can simulate that effect of wind indoors with a fan or just brushing across your seedlings with your hand once or twice a day.
RayR wrote: