Reeds are used in two-stroke outboards to control the fuel-air mixture. A bad reed can denigrate your boat's high performance, or worse, cause you to chase non-existent fuel and ignition problems.
As both composite and steel reeds age, they can become chipped, broken, or bent, and may not do their job properly. A broken OEM steel reed can tear up the internals of your motor. If a reed valve is malfunctioning, the fuel/air charge will not be effectively drawn into the crankcase. This can cause your powerhead to have difficulty starting, idle poorly, and/or not run at the top end.
Reed valves should be checked regularly in high-performance boating applications for proper sealing and lack of chipped material or cracks and changed for peak performance in racing applications after just a few uses.
There is no set time on when to replace reeds when pleasure boating, but the life of the reed depends on how many RPMs you turn and the actual type of reed material. If there is a gap between the reeds and the reed cage or if they are frayed/cracked, then replace them right away.
This graphic provides a quick test you can do for a leaky reed without having to rely on looking through an obstructed intake or removing the reed plate.