Need advice on yet another Spark Plug Change

I am about to change the plugs in my 2000 Mustang Convt...AGAIN...

I have to do this about every 15K.
And when I say I have to do this, I am not talking as some retentive person that has to keep this car at the very peak of performance. I mean that the plugs are so worn out that the car is miss-firing otherwise.

I changed the factory plugs at about 70K... It is now 115K. I have been using NGK plugs..which I thought were superior.
But these things are worn to the nubs and misfiring by 15K?

Mostly, we are putting highway miles on this car.
There simply has to be a better plug for this car than these NGK's.
I do not want to spend $10 each for a Platinum plug. I have tried these things in past cars and I never saw any difference at all in mileage or durability.
I am not looking for a gimmick here. I simply want a really good plug that will last.

I have considered the Bosch plugs at Autozone....but I thought they were supposed to be inferior to the NGK's.

Anybody have some advice?

Ive always used autolites in my motors.

No expert here but +1 on the Autolites. For some reason they seem to do the best in Fords.

you need to rum platnum plugs in it. go with either the autolite or motorcraft plugs. ngk plugs are good for the rice burners not for us cars. plus it will help improve you fuel milage as well.

i would suggest motorcraft plugs
i work at a ford dealership and we have seen many mustangs with autolight pluts that start to misfire

if the original ones can last for over 80k then y not use the same things