For all members the revenue from AdSense is shared for one year only. There are two exceptions to this -
1. Those who are contributing regularly and with quality contributions can request the Webmasters for an extension. That is, based on their contributions, the Webmasters may give an extension of 2 or even 3 years. So, effectively, you can continue to earn AdSense from earlier posts as per the date of posting.
Members who think they are eligible can contact Tony Sir. Refer: Extending revenue sharing period for active members
2. Editors get extended AdSense revenue.
There is also the option of republishing earlier articles (not posts from other sections) so that you automatically get the AdSense earning from it from the fresh date of the article (the date when you republished it.) However, note that you should not republish earlier articles which have not fetched any traffic at all and are thus not really useful to the site. Such articles will get shelved in the archives during the tuning process of old articles.
I would also advise you to read: Learn about the unique features of IndiaStudyChannel.com
When people come at you with their worst, you should come at them with your best (advice given to Selena Gomez by her mother, quoted in Time magazine.)
'Idhuvum Kadandhu Pogum "
Even this challenging situation would ease