Hi Sandra, Great question! There is no need to deploy the sensor for more than 24 hours in Recommend mode. We have developed patent-pending algorithms that normalize any reading that is less than three weeks to the previous three weeks weather data. So if you leave the sensor out on a cloudy day, but the previous 20 days were sunny, EasyBloom tweaks the light reading up to what it would have been if you left the sensor out a full three weeks. We spent quite a bit of time figuring this out, so you don't have to wait three weeks for recommendations. Cheers! Matt