The advantage is the fact that there would not be much issue if one gets an illness anytime in life.
Explanation:
Often, insurance companies do not give insurance to the people who are already in old age or have some serious ailments.
This is because they understand the cost in keeping that insurance is more than that they would be able to recover.
This can be done away with if the person takes lifelong insurance.
Then the company will have to pay for the expenses that come any time in the life of the person no matter any time until they live.