H1B Visa CAP exempt query

Hi,My H1 B visa approved in April 2012 and got stamped in March,2013.But due to some issue,I was not able to utilized the visa and got expired in Dec’2013.I believe same visa can file under CAP exempt for next 6 years. I want advice from you ,if I need to fill CAP exempt visa before April’2018 or can be possible for entire year 2018.Also if this time CAP exempt visa get approved in that case ,will I get it to utilize for next 6 years or it will end before 2018.Thanks in advance.Thanks,Ramesh Mishra+918975570229