As one of the many who have experienced losing a valve seat, I can tell you that overheating the engine has nothing to do with the seats coming loose. You will find that the common denominator on when/how this happens is when you have driven the car up to normal operating temperature and then shut it down. Do your shopping or whatever you were doing, restart the engine and it sounds like a can full of loose bolts. No overheating, no high rpms, not even driving. It happens at start up. When you rebuild/replace your heads, you must also replace the intake manifold as it is near impossible to remove all of the debris that goes into it. New factory intakes run $500. Most head and all engine rebuilders will not warranty the engine/heads without proof of the intake being replaced.
Here is some info on the differences in the early and late 5.7. The 6.1 and 6.4 Gen III hemi.
Gen 3 Hemi Cylinder Head Comparison