I HATE that cliche. Mainly because it's false. Maybe carbons don't bend like aluminums do, but they do wear out, lose their memory and warp. Some quicker than others. Not a single carbon arrow in my extensive collection is straighter than my worst cedar arrow.

Along with losing their straightness, they also break down with use and lose their spine. Again, some quicker than others. You see it much quicker if you select arrows that are right on the upper end of their spine range. That's why I always recommend bumping up to the next size if you wind up right on the top end of a shaft's spine range. With carbon, it's far better to be on the exteme low end of the spine range rather than the extreme top end. That is, if you want to use those arrows longer than a few weeks.

Besides, going to the stiffer arrows means you can add much more tip weight. Brings the arrow weight up to reduce your bow's noise and shock, and balances the spine range to your bow.