For how many months does a batch of bags of cement expires from the production date?

it is written on the bags but the atmospheric condition may alter the expiry date. if there is humidity than the bags will be expired quite quickly while the dry weather can take more time to expire the bags of cement. so also check the weather condition before storing the bags and try to make the dry storage place.

This is HUGELY dependant on the storage conditions. But average is 2 years. Also depends on the grade/type/quality and brand.