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You can do it any time.
You can create your own screens from scratch or copy an existing screen and tweak the parameters to tighten or loosen the criteria; add more filters.
Usually its good to relook at the screens every quarter, as many things would have changed. Also companies declare the annual results by Sep end and many do even later, so every quarter you will find new results of the same screens
Run the Guru screens every quarter; Run your won fav screens every quarter, create new screens as soon as you get hold of a new screening idea.