Ford's should have a light come on the dash to tell you when to drain the separator.
The maintenance schedule is kind of dumb. Check the Fuel/Water separator every month. Drain when needed or when the light comes on... How precisely does one check if they don't just drain it? So, is it drain it every month or when the light comes on?
There are guys on FTE who do it every oil change, do it every month, do it when the light comes on, etc... All of them have never had water, have had a ton of water or have had something in the middle.
You either trust the thing to do what it's supposed to do and tell you when you're supposed to do what you're supposed to do, or you don't. If the latter, whatever interval helps you sleep at night I guess.