(1) (a) The following term limitations apply to all bonds issued under 7-7-2301 (1). Except as provided in subsection (1)(b), bonds may not be issued for a longer term than 10 years.
(b) If the unexpired term of the bonds to be refunded is more than 10 years, the refunding bonds may be issued for the unexpired term.
(2) Bonds issued for any of the purposes designated in 7-7-2301 (2) may not be for a longer term than 20 years.
(3) The length of the term required must be estimated and calculated by the board of county commissioners, based upon the percentage of valuation of the property upon which taxes are levied and paid within the county as ascertained from the last-completed assessment for state and county taxes, taking into account probable changes in the taxable valuation and losses in tax collections. Irrespective of any miscalculation by the county commissioners in fixing the term of the bonds, the county shall from year to year make a sufficient tax levy to pay the interest and installments on principal on the bonds as the payments are due.