I have a lot of experience with coatings.If done right, and the correct type of coating it should last a long time.An old stroker VW engine i have has 75k miles on it with coated crowns and skirts,the coating is fine not lifting even on the one that had a little "issue" with a valve.Where the piston was impacted by the valve a little bit of coating is gone but you can't pick at it and get it to flake off.
If going the whole hog with coating this is how i would do it.
Ceramic coating,top of piston
Front of intake valve
Combustion chamber
Exhaust port
All of exhaust valve to where it sits against the guide
Piston skirt coating,
Piston skirt,
Underside of piston
Valve stems where it rides in the guide.
But all that being said if you keep heat in the chamber etc, you will have to reset your clearances cause the piston wont expand like before. Theres two places in the U. S where i'd spend my money on coatings are Polydyn in Houston. And Calico in North Carolina.Hope this helps.