This water timer has been reliably performing as expected. It comes on at dawn’s early light, even on overcast days, and shuts off when it is supposed to. If the batteries (2AA) go dead, the water stops. That means it is safe to leave the unit unattended. I have not used the device long enough to gauge battery life. But the batteries operate a solenoid valve; so it's reasonable to expect that the longer you water, the shorter the battery life will be.The timer was simple to install. No tools were needed. The unit’s connection is plastic and your hose connection is probably metal, so it’s prudent to use a bit of thread sealant, to prevent leaks.“Programming” the timer is as easy as turning the dial to the amount of time you want it to run. It will automatically come on the next morning. The only other controls are ON and OFF. They mean just what they say.This unit unquestionably restricts water flow somewhat. My watering scheme had two impact sprinkler heads linked together with 5/8” by 50-foot fabric hoses. When I added the timer at the water supply, the furthest impact head stalled. No amount of adjusting would get it going. Using larger diameter hoses or shorter lengths might produce different results. That solution was impractical for me, so I solved the problem by replacing the affected impact head with a gear-driven alternative.The timer comes with extra gaskets with wire mesh filters, which suggests you should periodically check the input connection for blockage. I would recommend this product.UPDATE: I encountered a quirk with this unit that I have not seen described elsewhere. An afternoon thunderstorm darkened the sky sufficiently to turn on the local street lights. When the sky brightened again, the sprinkler unit thought morning had arrived and dutifully came on. I manually turned the unit off, then re-selected the time duration. The next morning all was well. I assess no criticism or penalty for this behavior; the device reliably behaved as it is designed to do.