Your symptoms are close to what I just had with my 94 F 150 , I drive around 30 mins to work and after the engine would get warmed up it would sputter and sometimes stop. Then I could start it up and go for about another 10 to 15 mins and it would stop again. Took it to the dealer and they assured me it was a sensor bad so I pretty much replaced all sensors that are on the motor . Cleared up a few days then started back again and come to find out it was my MAP sensor that was bad .
I know its not a maf sensor but does pretty much the same thing , so it maybe that your Maf is dying.
Team Duratec #01,Sedan Revolution#4, Elder FocusedSlayer, Gump Crew 21
February 2012 Sedan of The Month