RTL_433 and unknown state of sensor

I flashed a LillyGo module with rtl_433, intending to use it with the cheap Govee water detectors. With auto-discovery on, the module found each device after it was triggered. I modified the sensor to show as moisture with a water icon and all five work properly.

I have them showing on a card in the Overview, along with the status of the Titan water valve they can trigger in an automation. After some hours, however, the sensors change from dry to unknown. I’m sure the devices quit publishing the sensor state to save battery. Is it possible to modify the MQTT code so that a longer period of time will pass before the sensor reads unknown? A month or more would be good; then I will know to check the device by pressing its button. Thanks for any help.