6. Set your messages to automatically expire
You can now automatically delete older messages with the help of iOS8, unless of course you are one of those people who like going through old messages and if you really need those conversations after a year, in that case don’t take this route. However, this option is much easier than manually deleting old threads.
Simply Go to Settings > Messages. Under Keep Message, select 30 days or 1 year.You can also adjust how long your video is stored or even your audio messages, and you can set them to expire after two minutes or never.