Well if you look at the following circular Item number 5
http://www.wpc.dot.gov.in/DocFiles/copcircular1.jpg
It states that you can renew your existing RTR ( A ) license for 20 years or for lifetime [ I believe you have an RTR ( A) and not an RTR ( P ) or RTR ( C ) ]
One of the criteria is operating an aero mobile service or an aero mobile station for atleast 30 hours ( it dosent say within 3 years )
OR
Satisfy the central govt by re-examination which i believe is what you just now did
Since you meet the above two criteria you shouldnt be having any problems getting a license for lifetime validity