You have 18 mths from the date of your first pass to pass all 14 written exams.Then from the date of your last pass you have 36 mths to pass a CPL and an IR.The exam credits are then valid for 7 yrs,but this is a rolling 7 yrs so every time you re-validate your IR you have another 7 yrs.To "unfreeze" your ATPL you need 1500 hrs total time of which 500 hrs must be on a multi- crew aeroplane and I think you also need 100 hrs night.