If you look at policy they have been very patient. They waited long time for taking over Hongkong and Kowloon. They are still asking Taiwan not to claim independence. They believe that in long they would either be able to persuade or force India to handover Arunachal and Laddakh to them. People who think that China can be persuaded to give off its claim on Arunachal are misleading people. Arunachal and Laddakh are important regions for buddhists. Without taking over these regions China cannot truly start its cultural superiority campaign. They are interested in Tawang only because its the seat of second most important Tibetans' monk after Dalai Lama.
India knows that it cannot fight China over either Aksai Chin or Arunachal. Indian Army is highly outnumbered in both the sectors. Also now with improved connectivity whole regiment of Chinese soldiers can be brought to Arunachal border from as far as Beijing within 3 days. Indian Army will need more than that time to move soldiers from Assam to Arunachal Border. Thats the main reason of China's belief that in due course of time Arunachal will belong to them. Indian government has not done anything to counter the claim, which only strengthens their belief.