> How long do dairy cows live? that depends on a number of factors. the average cull rate is about 30%. that means that if she enters the milk string as a two year old she would last a little more than three years. That is the average. I know dairymen who have cows in their 13th and 14th lactation. Mastitis, bad feet, and not breeding back seem to be the biggest reasons for culling cows. So the answer to your quest is 5 years on average but individuals can last as long 20 years.