Unlike incandescent bulbs that when failed are obvious, other types of bulbs are not obviously faulty though. When the ballast of a full sized fluorescent fixture fails, it's generally hard to turn on or takes time to flicker to life. For CFL I've seen them just take longer to start but that's kinda normal for the garbage swirly bulb. LED report life of 15+ years but that's typically when they expect something to stop producing light (either the driver fails, the elements burn out, etc). For X10, lifespan means also when the bulb starts becoming electrically noisy. I have looked for information on whether this type of failure is built into the reported 15 year life span, but it's tough reading to understand. It's frustrating for X10 (a small market) but it's also problematic for high end audio/video and other applications relying on clean power signals. I'm surprised there hasn't been more talk about noise unless this failure mode (creates light but also electric noise) is extremely rare.