Carbon fiber is extremely durable and flexible, and provides a much more comfortable ride than steel. It will crack if you put it under extreme duress, but steel welds can do the same thing too. As long as you aren’t wrecking on the bike regularly carbon can last a lifetime. There are ways to repair it too but it can be very expensive. Red Wings are hands down the best. I’ve had a pair for 20 years and only had them re-soled once. They are so damn comfortable and soft after all this time.