The default value for AutoSweep Parameter which invokes XPSSweeper is once per week. But as per the CA document, CA recommends this to run once per every 24 hours.
If the XPSSweeper utility does not run often enough, the Policy Server could have trouble starting. Too many tombstone objects in the policy store produce the following error:
If you are importing objects by using the SDK you should run the XPSSweeper after every Import to synchronize legacy objects with XPS objects.
It is not recommended to run XPSSweeper more frequently than every two hours, even when scheduled because of PS cache updates.
There is no magic number and it depends on your environment.
After each SDK Management script run to synchronize legacy and XPS objects.
It should not too often as it can impacts performances. Would need to be a trade off in your environment