I usually make kefir at night. Because the fresh milk is cold from the refrigerator, I'll set the jar in front of a heat vent to warm a little. At night our thermostat is set to 62 degrees F. In the morning, the bottle will have warmed to 75-80 degrees. I then move it to a counter top, out of direct light. By the next evening, it's ready to process. If I don't have time or if it's not ready, I'll put it in the refrigerator to slow fermentation down. Then I can process it when I have time. I have found that if the kefir stays warm for several hours, it will be ready in as little as 10-12 hours.