I've had mechanical timers controlling outside Christmas lights for many years, before I started using X10, with no problems. I use small (approx. 12"L x 6"W x 5"D covered plastic boxes. I cut small notches in each end so that wires can come out with the lid closed. The timer and the wires connecting to it are in the box and the lid is taped shut with duct tape. One wire goes out to a weatherproof external outlet and the other wire goes out to the string(s) of lights. After the holidays when the weather permits, I put the boxes back in the basement for the next year. My mechanical timers died this year. Sounds like time for X10 modules to replace them.