Originally Posted by
old's'cool
By the same token, with an educated guess as to the realistic maximum number of cycles a component may be subjected to in its expected lifetime, a component can be engineered to have a fatigue limit that is close enough to infinite that nobody will know the difference, unless something goes wrong like the designer screwed up or it wasn't applied according to the design specification. I suspect garage door springs and bicycle spokes fall into this category.
The fact that I have had to replace all the springs on the 5 garage doors that I've owned at least once appears to say otherwise. Likewise the fact that the local hardware store has always had a good supply of replacement springs on display in a fairly prominent location.
OTOH, my luck with bicycle spokes has been better (with the exception of one tandem wheel that I finally gave up on and replaced). The spokes have generally lasted as long as the rim and in some cases have made it through one or two rim replacements. So they've at least held up for one or two hundred thousand miles.