talking with my hubby about building a homebrew cabinet incubator, he suggested wiring 2 lights in series rather than parallel. what this does is decrease the voltage of each bulb by roughly half, but at the same time increasing the life of that bulb significantly... so if you have 2 100 watt bulbs, each one will run about 50 watts, and the constant on/off won't bother it at all since it's nowhere near it's capacity. you're best using 2 bulbs of the same size, to maximize the efficiency btw... depending on your incubator build, the ideal would be to have the bulbs on as long as possible and off as little. you can test this by varying your lightbulb sizes. if it comes on for just a few seconds and off much longer, you're too hot and more likely to get temperature spikes. of course, you also want to make sure it's insulated very well, or else the bulbs may stay on all the time and never reach temperature too... it's a balancing act. here's the wiring diagram he came up with, with some explanations. there is no fan or turner in the diagram, as usually they would be wired independently anyways. this is just for a thermostat/2 lightbulb setup (in series, not parallel). a parallel setup, if you use 60 watt bulbs, both would run at 60 watts... but again if you decrease the voltage going to each bulb, you'll increase the life of them, and have fewer worries about a light bulb burning out during incubation.