How to get more validity for data card plans (Reliance)

This is the data plans currently available for Reliance Net connect Broadband + users (03.10.2011)

In the above plans if you recharge 715 Rs you will get 1 GB with 30days validity.

Bu what i am doing is first i will recharge 200 Rs So i will get 1 GB with 7 days validity. After 6 days I used only 300 Mb and i have 724 MB balance Now i use 180 Rs plan I will get 250 MB with 30days validity + 724 MB.

So totally I spent 380 Rs to get (1024 MB +250 MB) with 36 days Validity.

Hope It will help you.