I fully agree that 466°F CHT is criminally high, even if Lyc 'approves' it. Engine longevity is not one of their priorities apparently.
On a TCM IO550 engine, somewhere in the 420-430°F range a thermal runaway will occur if the CHT's are allowed to go that high. What happens is that the cylinder gets heated unevenly and becomes oval while the aluminium piston inside stays round. This will cause scuffing and because of higher friction, more heating will occur, with more scuffing until after a short time the cylinder and piston will be damaged.
This phenomenon was observed on an instrumented engine with eight (8) CHT sensors around the circumference of every cylinder.
Even with a JPI you have only one CHT probe per cylinder. So, when the runaway heating occurs, it is too late already and only a massive power reduction can save the cylinder.
My personal CHT limits are 380°F for operation with 400°F as a never exceed limit (do something right now).
This is an area where the manufacturers redline doesn't mean a thing, it was determined when the manufacturer could prove to the FAA that his engine would not go into detonation at this CHT level. This is on an engine test stand with each cylinder individually cooled by shuttered air hoses, an optimal condition never achieved in a real cowling.
It looks like the Lancair builder will have to spend some more time on baffling, cowl flaps, etc if he wants a long life out of his engine.