I don't know what the OP means when he says
I want to invest in health insurance from now on so that I can use the policy after I retire.
Generally, a health insurance policy covers costs incurred during the current calendar year (or specific period such as July 1 of one year through June 30
of the next year) and does not cover future periods. Indeed, many policies
do not guarantee renewal when the current period ends (with exceptions
for employer-provided coverage through COBRA in case employment ends).
So investing in
a health insurance policy meaning that you pay the premiums now, and
the insurance company provides the policy in the distant future is
something that is new to me. Besides, what will the policy include?
If someone had bought such a policy many years ago, say, before
CAT scans and MRI were developed, would the policy cover such new
developments? Or the policy would cover only those procedures,
tests, and medications that are available when the policy is written
and the insurance premiums start to be paid? The long-term health
of the insurance company is also of some concern. When something
is offered to me with a lifetime guarantee, I skeptically ask,
"My lifetime or the device's life time or the company's lifetime?"