As far as I know, there is no restriction that the deduction for self-employed health insurance is limited only to premiums paid for "the period for which you were self employed." If you are self employed, for this purpose you are considered self-employed the entire year and can treat as a self-employed health insurance deduction the entire amount (limited to net profit from self-employment reduced by the deductible portion of self-employment taxes and any self-employed retirement contribution such that the sum of the amounts on Schedule 1 lines 14, 15 and 16 does not exceed net profit), provided the policy is in your name or the name of your self-employment business and you are not eligible to participate in your or your spouse's employer-provided plan.
Section 162(l) says:
(l) Special rules for health insurance costs of self-employed individuals
(1) Allowance of deduction
In the case of a taxpayer who is an employee within the meaning of section 401(c)(1), there shall be allowed as a deduction under this section an amount equal to the amount paid during the taxable year for insurance which constitutes medical care for—
(A) the taxpayer,
(B) the taxpayer’s spouse,
(C) the taxpayer’s dependents, and
(D) any child (as defined in section 152(f)(1)) of the taxpayer who as of the end of the taxable year has not attained age 27.
Note the phrase, "the amount paid during the taxable year."
