He's referring to the plastic cooling system. ALL of the plastic cooling components will fail, and for 99% of us, this happens all around the same time.
This includes the thermostat housing, plastic pipe from the engine block to the housing, the degas bottle (coolant bottle), and hoses. Doorman sells these components for a fraction of the cost of Motorcraft, but many have had issues with the cheaper parts. Word of advice, any non-ford replacement parts are almost guaranteed to be worse than junk.
My V6 has lasted much longer than my V8, the original components appear to be holding up well. But when you begin to overheat, it is time to change ALL of the components at once. Not so bad on the V6, but changing them on the V8 sucks.
Also, you will eventually need new coils. More often than not, non-ford coils are a waste of money and fail within weeks or months.
Anyway, welcome to the forum - you've got an awesome car!