An advance made under RCW 39.34.130 through 39.34.150 from appropriated funds shall be available for expenditure for no longer than the period of the appropriation from which it was made. When the actual costs of materials and services have been finally determined, and in no event later than the lapsing of the appropriation, any unexpended balance of the advance shall be returned to the agency for credit to the fund or account from which it was made.