Validity of a blank signed cheque

Hi all, I have been a victim of fraud by my manager, he uses some of my signed chqs and draws money from market against them and still many cheques are missing, and also he issued cheque book from bank by forging my signature, and now around 70 chqs are missing, i want to know if cheque book is printed in mar2013, then how many years it will be valid to be presented in the bank. Regards