Government ensure availability of urea throughout the year at affordable price to the farmers across the India, to ensure food security, hence government support farmers by providing subsidized fertilizers at affordable price since 1977 through various subsidy policies implemented time to time.
Government monitors all the steps from manufacturing to till application at field through their apps called mFMS / iFMS.
Current policy NIP 2012 / NIP 2014 clearly says a period of 8 years but Government will continue to support farmers to provide fertilizers at affordable price even after 8 years either by extending the same policy or by introducing some other subsidy policy. Since urea share is around 70% of total fertilizers, hence cannot be ignored.
Since MRP is fixed by the government of India, hence MRP of urea will be according to govt. policy at that time.