Most residential irrigation systems are installed using non-latching valves. Latching valves are more commonly used with battery powered irrigation controllers in remote areas where commercial power is not readily available. The fact that your system was using a Rainbird ESP-6TM also tells me that your valves are non-latching, as that controller is incapable of controlling latching valves.
These valves also do not have motors in/on them, they are operated by a spring loaded solenoid. The power from the controller energizes the solenoid allowing water to flow thru the valve, when the valve loses power it will close.
As for reliability, I’ve been using a model B located in the garage for 2 years with no issues using the interval program. The only trouble I had originally was with the wireless connection due to the distance from my wireless router. I solved that by using powerline adaptors to connect the RasPi via ethernet.