Very interesting question. I would like to discuss my experience about coolant which I thought was lifetime coolant. After driving almost 125,000 miles, the coolant in my car was almost null. It never came in my mind to refill it. And gradually, the engine startd overheating and the hoses and radiator were damaged. Since i didn't refill the coolant, i ended up replacing the radiator and hoses in my car which costed me lo of money. So, i would like to advice everyone that refilling the coolant after every 100,000 miles is really important. Don't miss that.