"Grapheme is stronger than steel"--of equal thickness, weight, or some other characteristic that the statement is based on. Reminds me of the hype surrounding titanium--"stronger than steel"--of the same weight. A heat treated part made of equal thickness steel as a titanium part (other specifications aside), will be at least as "strong," although it will also weigh at least 1/3rd more. But, back to the original post--it's pretty much a given that lighter, thinner, stronger materials of any ilk, while likely performing at a higher level by some metric than their heavier counterparts, will also break more easily, although not in the same way, in most cases. Graphite rods seem to have a virtually limitless lifespan, if you measure their flex characteristics when new, then again after years and thousands of hours of use, compared to glass and bamboo (partially due to glues/resins, no doubt), but they fracture much more easily from impact damage and excessive overloading, and do it in a much more catastrophic and spectacular fashion. Fishermen just have to decide which characteristics make the best rod for them and choose accordingly, accepting the bad with the good for whatever material they select. I've broken glass, bamboo, and graphite rods, and I've had (older) glass and bamboo rods soften up over time--still, I can't say one is unequivocally "better" than the others.
CC