I often get 100,000 miles or more from factory plugs . But I have not owned a Ford in years .
Right now , I am driving a 2014 F150 w/100,000 + miles . It is a company truck . Only thing I do to it is out gas in it , get the oil / filter changed every 3,000 miles ( dino oil ) and drive it .
If it needs work , I take it to the shop of the boss's choice .
As far as yours , I would replace plugs as needed , bur I ask if the CEL has come on at any time .
Check all the plugs and fluids . Check , visually , all your sensors ( including O2 sensors ) . Are you using " good " gas or the cheapest you can find ? Ethanol / gas mix or pure gas ?
Is most of your driving city or open highway ?