TCNs are taking long time to expire

[UdhayaRB]

We tried to exchange TCNs between two android devices. Although we got a new entry every 15 minutes, we observed that the previously generated TCNs are not expiring timely. There are few TCNs that are prolonging for more than 15-20 mins and even more than an hour.
Steps:

1. Run the app on two android devices
2. Pull the USB cables
3. Put the devices to sleep and check after 6 to 8 hours.

Actual Results :
Some of the generated TCNs are not expiring within 15mins

Expected results :
All the generated TCNs should expire within 15mins