as you know our Texas soils are constantly on the move. I can drive anyone by several concrete fences that have broken in half with the contractions and expansions of the soil.
Concrete cannot move around, therefore it will just break at its weakest link.
One one park near where I live, the City installed that concrete aggregate paneled fence. Where you have your king posts with slots and you just slide in these panels. Well, the posts gave a bit enough for the panels to disengage from the grooves and therefore just fell off.
I would again, seriously evualate your decisions on material.
Wood fences, even with metal posts do give to a large extent and can be repaired. Usually like your foundations, if you keep the posts around a gate watered, you will not have any problems in June, July, and August.