Hey @jaydons
You are correct, sort answer is the default index set can be configured different ways.
The index will rotate as it was configured, this is called rotation strategy. three settings ( size, time, count).Then below that setting you have Rotation period. Tthis setting would be for hour, day, week, etc…
Remember the more indices you the more volume will be used. TBH you may want to read over the documention.
hope that helps.