Did you keep the original coils for spares?
I have never seen a service interval on coils. Mine is a 2008 with 286,000 miles and still has the original coils. I am a little surprised it never had one go out yet.
Maybe in the summer when I have time to play with the truck I can switch out a few of the old coils at a time, to see if one of them actually is bad, or if it was only the plugs
I'm still not sure about the markings on them, it looks suspicious to me