I did yesterday. The bolt that clamps the seat to the seatpost snapped in half during a race. The whole assembly just sort of exploded all over the race course. I wouldn't have minded so much if it was later in the race, but it was on the third lap, and I was just getting into my groove. The disturbing thing is that there was absolutely no warning before hand.
So now I'm kind of questioning the serviceability of the rest of my components. I've been running the same bike for five seasons. I've never really followed any sort of replacement schedule for components -- when they break, I replace them. But having your seat suddenly disappear while riding over a bumpy course, and leaving nothing but a pointy aluminum post pointing skywards kind of gets me thinking.
So, should one routinely replace such items, or should this event be considered more or less an anomaly?