If any sewage district in any township in any county in this state has heretofore issued bonds for the purpose of paying the cost of constructing sewers in lateral sewer districts within the said main sewage district, which said bonds were issued to mature during a period of more than twenty-five (25) years from the date of issuance thereof, instead of within twenty-five (25) years as provided by law at the time of the issuance of such bonds, and such bonds were otherwise legally issued, such bonds are hereby declared to be legal and binding obligations of said sewage district and are hereby validated.