Ordered and deployed 5. The corded accessory is great to shove under an appliance … when wet is indicates mostiure. They say the battery lasts 3 years (will see). ZHA picked them up right away. Bearded Tinker metnioned them, and I grabbed them.
You probably mean the Sonoff SNZB-05P ? 
Thank you for letting us know.
They even claim a battery life of over 5 years
Yes, thats correct.
So how is your long Term experience with that sensor. I deployed one yesterday inkl the extension cable and directly got massive false alerts.
Remove the cable and see if the false alarms still happen. The extension cable could be the cause (high humidity may trigger false alerts, or just a quality issue you can contact sonoff for a replacement)
Yeah i removed the cable couple of days. Since than i have no more Problems with the sensor. I quite liked the idea of the extension cable but it gives me to many false alarms.
The extension cable contains two separate wires wrapped in nylon.
External force or improper protection during shipping may loosen the nylon wrapping, causing the wires to short and trigger false alarms.
You can contact SONOFF for a replacement cable.