Any policy containing a provision for a deferred annuity on the life of the insured only, unless paid for by a single premium, shall provide that in the event of the nonpayment of any premium after three full years' premium shall have been paid, the annuity shall automatically become converted into a paid-up annuity for such proportion of the original annuity as the number of completed years' premiums paid bears to the total number of premiums required under the contract.
Neb. Rev. Stat. §§ 44-372