I would take a strong look at the coil. I had a bad coil on a Tempo that would work until hot then shut down. Let it cool and off it went, Town driving is generaly harder on a car because you do not get the airflow of highway driving. This can cause the engine and engine compartment to run at higher temps. The problem with checking the coil after the car has been sitting is that it will read fine. The check needs to be done as soon as the problem shows its head. Good time to get burned, so take precautions.

Good Luck Dan 96 SE 2.5 V-6 89 Silverado 4 x 4 with snow plow no rust