How do I configure the graylog history to keep for 3 months? I stayed and it only shows logs for 27 days.
The docs page for all those settings, but its simply a combination of index rotation (how often we create a new index) and index retention (how many past indexes do we keep)
https://go2docs.graylog.org/5-0/setting_up_graylog/index_model.html
The easiest way to guarantee you have the number of days retention you need is to set the rotation strategy (how to decide when to create a new index) set to Time Based, with a Rotation Period of P1D (Period- 1 Day).
Look for these settings in the index settings in System/Indices page. Click the edit button next to the index you wish to change and look for the rotation and retention settings towards the bottom of the page.