Insurance policies can only be issued one year at a time, because the data used to make insurance policies depends on what medical problems you had in the previous year (and if you survive the previous year). You cannot buy a health insurance policy at age 20 to age 80, so in the same way you cannot buy a medical insurance policy any more than one year in advance. You will, however, need to make sure you renew your health insurance policy to prevent any lapses, since if your health insurance policy lapses, your residence permit could be canceled. But in actuality, if it does lapse, you can just pay the amount due (including the period when it lapsed) and renew it. The immigration office would probably never know.
