By default, the Nexus One limits text messages to 200 messages per conversation. You can change this value to one that better meets your messaging needs.
1. Open the Messaging application.
2. Select the Menu key.
3. Select Settings.
4. Select Text message limit.
5. Use the + and – to change the value to the desired number or tap the number and use the keyboard to input the desired value.
6. Select Set.
