Script Rotation Interval controls when Substy may close a stale or paused selling sequence so another eligible script can be selected later.
You need permission to edit AI settings for the selected creator. This setting has no additional paid-plan requirement.

Open AI Chatter and choose General.
In Behavior Settings, find Script Rotation Interval.
Enter a whole-hour value from 8 through 24.
Leave the field by clicking or tabbing elsewhere. The value saves when the field loses focus; there is no separate Save button for this setting.
The interval can make a stale or paused selling sequence eligible to close so a script can be selected later.
It does not force an active conversation to switch scripts when the chosen number of hours is reached.
It does not promise a different script. The next selection depends on what is eligible for that fan.
The value did not save: enter a whole number from 8 through 24, then leave the field.
A conversation did not switch at the selected hour: active conversations are not forced to change, and the next script still needs to be eligible for that fan.
Editing Script Rotation Interval requires permission to edit AI settings for the selected creator.