Lighting contacts are the way to go for this application. They are designed for the constant on/off that lights do every day. As for the Siemens, I do a lot of work with Siemens, but don't think I can honestly recommend that someone pays money for their stuff. We have extremely high failure rates on many of their products. I am not saying I wouldn't use their stuff (because we have a lot of things that I will be using of theirs for automating my tank) but I would definetly check other options.