My oldest COP is 3 years old. I replaced all the plugs at the same time, and replaced each plug when I replaced the coil. And I have replaced plenty since then. When they fail, they always set a pending code. I think it needs a heavy dose of seafoam and an italian tune up. Did a few full throttle starts with seafoam and it is doing better. It may be carboned up due to my grandfatherly like driving. I haven't towed since June.
BTW, here is an interesting post on FTE forum about ways to keep water out of the spark plug wells.
http://www.ford-trucks.com/forums/1185557-getting-water-on-your-plugs-heres-the-fix.htmlAnother technique is to liberally grease the tips of the boots to slow the water wicking process that destroys these coils. One guy added an o ring on the COP.
