My heater will not get hot it blows barely warm air

3 to 5 years normally but they can go bad at any time.you can get a truck off the show room fllor and have the heater core go out on it 3 days later,,,,it just depends on how you drive them i guess

It is true That a heater core can prematurely go bad. I am not so shore that your driving style has anything to do with the length of time it lasts. What makes you think the heater core is your problem Sound to me like your air temp mixer flap actuator is a more likely cause for the symptoms you describe. If your heater core were bad you would have an antifreez oder in the cab of you truck and your windows would fog up. Other times they will get dirty and restrict air flow this would not cause the temperature of the air to be any cooler but instead reduce the amount of air you get.