How very thoughtful of your husband! Seedlings and flowering houseplants really need the additional light from a grow light and the closer it is (3 to 4 inches) to seedlings the better for the young plants. However when it comes to sedums and succulents like the Echerveria in the photo you sent they prefer to go dormant during the cold days of winter and can survive in dry soil and low light so the light can be 10 to 12 inches from the top of the plants. As far as daylength (lights on) this again depends on if you want the plants to be dormant and not stretching for sunlight (like those succulents) or if you are trying to grow seedlings or flowering plants. I would start by having the lights on for just 8 hours a day then increase to 10 hours in the spring as the weather warms. Don't worry about keeping the garage warm as cool temps will help your succulents stay dormant. As long as the plants do not experience a freeze they should survive until you can put them back outdoors in May. Keep growing, Marianne Binetti P.S. Thanks for following me on Instagram!