I apprenticed a number of years ago on a small farm with a woefully undersized but beautiful old glass house where we propagated all of our vegetable starts. I learned a lot in that glass house, hand watering the seedlings every day, making sure it was opened in the morning for ventilation and closed in the evening to keep the heat in, mixing up potting soil and seeding tray after tray.  Andy, the farmer, rigged up a system to automatically water. It worked for a while but one day in summer, we came to check on the seedlings, after having been distracted for a day or two, and they were just about dead. If I remember right, the battery in the timer had failed. That memory sat with me for years and, determined to never let that happen again, I stayed away from automatic water for a long time.