As a team a lot of our days are now spent talking about OMS, one key OMS change recently was to enable the retention of data for more than the typical 7 , 30 or 365 days. You can now go to 2 years if required. See the blog from Richard Rundle that tells you how: https://blogs.technet.microsoft.com/msoms/2016/11/15/search-for-up-to-two-years-of-data-with-oms-log-analytics/
The GUI will be updated later to do this in a less manual way.
UPDATE: the GUI has now been changed
To change the length of data retention:
- Sign into the Azure portal.
- Browse for Log Analytics and then select it.
- You see your list of existing workspaces. Select a workspace.
- In the workspace blade under General, click Retention.
Use the slider to increase or decrease the number of days of retention and then click Save