Its very clearly mentioned on the DGCA website
(c) Renewals mandatory at IAM/ AFCME/ MEC(E). The following medicals will compulsorily be done only at IAM/AFCME/MEC(E):
(i) 4th renewal upto 40yrs of age,
(ii) 7th renewal after 40yrs of age,
(iii) All medicals after 60yrs of age and
(iv) Medicals after attaining age 35, 40, 45, 50, 55 and 60 yrs.
CLASS II MEDICAL EXAMINERS LIST