My opinions lean toward research and what past experience has shown.
Most of the time what designers use has already been used in different applications.
The stock spark plugs are plated and they need not to be coated with anti- seize grease because depending on the type you use the torque specifications are changed (reduced) yet I have found that the only time I have had a spark plug backout has been when using anti-seize.
Effectively NGK does not want you to use ant-seize on their plated spark plug threads.
I would recomend checking the torque settings of your spark plugs before a long trip or if you have used any type of lubricant on the threads when installing them.
Some of my friends are engine performance buffs (gearheads) and everyone at one time or another brings up the ignition subject, hotter plugs or, colder plugs, design variances, wire sizes, timing, sensors, computers, etc...
With spark plugs there are several determining factors surounding design and applications but they follow a few basic guide lines that should be considered.
Combustion chamber design.
Engine compression ratios.
I use the phrase "driving habits" in a broad sense; to cover where and how you drive, and that includes traffic and terrain.
With Toyota the Japanese business ethic doesn't compete domestically but internationally and abroad.
It is nothing new for them to obey restictive emmision laws and follow another countries regulations because Japan's own laws have been shown to be demanding in compliance.
The spark plugs that come in their vehicles are in compliance to fulfill
regulation testing standards and warranty standards, and the brands that are used also cover the regulations for fair economic practice laws set in place by their country.
Anytime an ignition component is changed from what is common design in a vehicle, the ECM to recognise the change should be reset if it is desirable to expedite the behavior and adaptation process. (disconnect the negative battery cable from the terminal for 3 to 5 seconds)
It then takes appoximately 50 miles of drive time for the ECM to adjust efficently.
One of the steps that is outlined when either testing or replacing
electrical and ignition components is to disconnent to battery for the duration of the job performed.
Touching the negative cable to a common ground for a few seconds after disconnection from the battery also helps capacitive discharging of the system.
One of the reasons spark plugs don't last longer than we wish they would is because they loose their efficentcy from wear on the electrode edeges from the stress of the electrical currents ability to jump from the center electrode to the side electrode and the right angles that are manufactured into the plugs design.
Through the convection of heat by compression in the combustion chamber and the rapid cooling from the air fuel mixture over repeditive cycles, the plugs litterally loose their edge.
When the electrodes designed efficentcy is compromissed the electric current has a natural tendancy to find the path of least resistance in order for the current to travel to it's polar end.
The current when facing resistance finds other points of collection to travel to and the direction of the spark developed can retard the combustion cycle and cause an incomplete burn and build carbon deposits which the carbon itself can retain heat and prematurely ignite the fuel mix causing pre-ignition/knock which further retards the ignition sytem causing fuel to be wasted in a effort to correct itself by restricting the spark plug from firing, cooling the affected chamber .