Our original Turkish PAYG had a similar way of operating - if left for more than 60 days without being used or topped up you then had to do another top up and it would be reactivated, but the previous amount of credit was still there and could be used.
Friends who bought a SiM card last year have near the same as above - but they have a 6 month period before the phone is deactivated.
So may depend on the original package that was purchased with the SiM.