I don't know a everything about ceramic coatings but let me try my best.
We do coat piston tops and sometimes the ex housings but that is mostly for cosmetic reasons.
I have been using Swain Tech with pretty good results. I don't know how much it is helping as I've only not used it one time (piston coating). I figure it as insurance.
J222, you can melt ex valves and really raise egts by going too conservative on timing.
I've really had a lot of luck by using Performance Trends Engine Analyzer 3.9 to get my timing curves. I truly think it has been the difference with us keeping things together and making big power. I highly recommend this product. Kenny Duttweiler uses it so it must not be too bad.
I have yet to melt a piston or have any major problems. I have warped a few ex valves but we don't worry about this too much. We have learned not to shut down the engine too fast and that solved a lot of our problems. Now when we warp a valve, we just run her hard again and beat it flat again and it usually fixes it again as evidence of the leak down test. We have been using the Ferrea inconel ex valves with pretty good luck. We have also not ever seen any hint of detonation in the last three years.
I also highly recommend an on board egt gauge hooked up to a warning light. Set it at 1650°f for supercharged cars or 1800°f for turbo cars If you see the light, abort the run. Fix the MAP and try again.
Of all the things I've mentioned, the computer simulation with Engine Analyzer 3.9 will make the most difference on durability.
http://performancetrends.com/download.htm#eaproI'm not big on water injection. Water make steam which displaces usable oxygen in the chamber and robs power but it will bring egt's down.