All civil actions for malpractice or professional negligence against architects or engineers duly licensed or registered under Title 32 shall be commenced within 4 years after such malpractice or negligence is discovered, but in no event shall any such action be commenced more than 10 years after the substantial completion of the construction contract or the substantial completion of the services provided, if a construction contract is not involved. The limitation periods provided by this section shall not apply if the parties have entered into a valid contract which by its terms provides for limitation periods other than those set forth in this section. [PL 1975, c. 434 (NEW).]