The main concern that I told him about is that if he leaves his current job and then develops a pre-existing condition, he may not be able to easily get life insurance coverage in the future.
However, I want to quantify the chances of that happening. I'm wondering how I could do that.
Since each person has his own specific risks associated with approval for life insurance, such as, health factors and family health history, and you can't really anticipate future health issues that have not occurred, it wouldn't matter what his chances of being declined for life insurance are, if he just goes ahead and applies for his own individual life insurance policy now. He can always cancel the policy or not pay for it, if he doesn't want the coverage.
But, once he is approved and the policy paid for, he has the coverage in force.
A life insurance plan through your employer should supplement what you have on your own. It's foolish to only have life insurance coverage through work, because people die between jobs, lose their job, or their employer goes out of business.
If he gets his own life insurance policy then he 100% wouldn't need to worry about not being covered in the future if he lost his job.
Also, if he is declined for his own life insurance policy, he can try getting guaranteed acceptance life insurance coverage which may cost more, but it does provide some protection.