What are best practices for set up of Sourcing rules/Assignments for Std PO

We use both ASCP and entered requisitions to generate Std purchase orders.    Are there any documented best practices when setting up sourcing rules and assignments?   For example-

if Sourcing depts. do a lot of sourcing changes of suppliers over a plan month for a given SKU,  should they create new sourcing rules, create multi-ranked Sourcing rules and change the ranking, manage the supplier through multi-ranked rules + setting capacities on the supplier's ASL?