29 CFR 453.17: Term of the bond.

The amount of any required bond must in each instance be based on funds handled “during the preceding fiscal year,” and must be fixed “at the beginning” of an organization's fiscal year—that is, as soon after the date when such year begins as the necessary information from the preceding fiscal year can practicably be ascertained. This does not mean, however, that a new bond must be obtained each year. There is nothing in the Act which prohibits a bond for a term longer than one year, with whatever advantages such a bond might offer by way of a lower premium, but at the beginning of each fiscal year during its term the bond must be in at least the requisite amount. If it is below that level at that time for any reason, it would then be necessary either to modify the existing bond to increase it to the proper amount or to obtain a supplementary bond. In either event, the terms upon which this could best be done would be left to the parties directly concerned.