"Many if not all insurance companies will cease to cover you once you qualify for medicare so I doubt many have a choice.
Correct me if I am wrong on this please and insurance companies will continue to extend normal benefit policies after a person qualifies."
Forgive me for not being able to figure out how to post your reference in the nifty blue box as this is my first contribution to this site.
If you are actively employed and carry insurance, the insurance you have is primary to Medicare, regardless of age.
If you are a retiree, with retiree benefits, Medicare will become primary, and your benefit plan would be secondary.