aluminums are more susceptible to failure than steel because they can only take so much more stress...no one can actualy determine how long aluminum will last for rods because they can vary from one full RACE season to over 20k miles on a vehicle...but if your rod fails then the rest of your engine will so a lot of people will replace them after 1-2 race seasons (1-2 years) it's NOT wroth the investment if you don't even know this, stick with steel and only go aluminum if your pockets are deep