How will the validity of each city-specific Max Pack work?

Since each Max Pack is a separate purchase, they will each be valid for 12 months from the date on which you purchased them. For example if you purchase the Delhi pack on March 15, 2017 it will be valid till March 14, 2018. And if you then purchase the Mumbai pack on April 1, 2017 then this will be valid till March 31, 2018.