I looked at the plan details on the Jio website. To me, it seems as though first time recharges of any value after July 11th will be getting the increased validity based on the recharges (56 days for 309, 84 days for 399 and so on) only for that first recharge and after that every plan will have the normal 28 days validity. (Atleast that is what the T&C seem to imply). Or in simple terms, the increased validity available on different plans is a one-time offer (ass of now) and any subsequent recharges will have the normal 28 days validity.
Looking to the Jio CC for answers is wasting your time because their answers seem to change every few days depending on what briefing they have been given. (I was told earlier by various CC members that all these new plans with higher validity will be available for multiple recharges through atleast Apr 2018 while now the T&C on the Jio website says only for 1st recharge). If that is not the case, then seriously why does Jio have to complicate things so much.