The provisions of sections 407.850 to 407.885 shall apply to all valid contracts now in effect which have no expiration date and are continuing contracts, and all other contracts entered into or renewed after September 28, 1987. Any contract in force and effect on September 28, 1987, which by its own terms will terminate on a date subsequent thereto shall be governed by the law as it existed prior to September 28, 1987.