twin plugs are used in small A/C because if you foul a plug you have another source for combustion (dual Mag Ignitions also that do not need batteries to fire) this is a safety issue because you can't pull over to a cloud and jump out and change them. A side note is that the plugs fire from separate points in the cylinder and because of that the total fuel mix burns in less time and all the power that is generated is applied to the piston when it is at a higher point in the barrel where it can generate more power.
Since the twin plugs can burn it in less time, less heat is generated over time and the engine can run cooler.
yes the laws of electricity include following the path of least resistance. The mult electrodes just mean more places to choose to go. Yes, they will probably last longer. I doubt that they will last 4 times longer (Because they cost 4 times longer) though.
I change my plugs in my toyota ever 100K miles whether they need it or not
(It has 367K miles on it) It cost me 4 bucks and I am off again.
racers will often indicate the plugs so that the electrode will be facing a wall and the open gap faces the chamber so not to block the spark with the electrode.
don't get sucked in to the more is better deal it is all crap in my book......BTW I once was looking at a pic (in a mag) that had a split fire plug that showed the plug firing. The tip was completely (both electrodes) lit as well as shooting the flame up though them...........really looked cool and powerful. the small print said "for illustrative purposes only" makes you wonder why they could not get a real picture of it doing it.
hope everyone had a nice day yesterday.
steve