I did a quick check on IATA's visa & passport tool with some made up data for a Turkish citizen born in 1980. I didn't get an indication that you are only allowed to stay up to three months. It was even mentioned that 10 year multi entry visa exists. When you have a multi entry visa you are apparently only allowed to reenter if you haven't been in india for more then 60 days. If you want to reenter earlier it is stated that you should contact an Indian mission.
To be sure, you could try to fill in your details and see the IATA advise.
With that information you could then try to verify with an Indian mission in Turkey.