The dry out time could be as little as 4 hours depending on the weather conditions (temperature and humidity) and the rain threshold that is set. If the weather conditions remain cold and damp, your sensor could be active for months.
Hunter Rain Sensors and Solar Syncs have two separate options for setting a rain shutdown threshold:
The Mini Clik uses a spindle adjustment to set the amount of rain you want the sensor to witness before it shuts down the system. This amount can be set by adjusting the spindle on top of the sensor and the range is 1/8" (3.17mm) to 1" (25.4mm).
A vent ring around the base of the Mini Clik's spindle assembly can be used to prolong the sensor's dry out time. Exposing more of the internal dry out rings will naturally dry the sensor out faster than if the vents are closed.
The Rain Clik and Solar Sync models come equipped with a Quick Response feature that shuts the system down upon contact with the first increments of rainfall.
The Dryout setting would need to be determined by your site. Turning the top vent ring will open or close the vents. When opening the vent ring, disks will dry out quicker, and irrigation will resume quicker.