QX4 coil pack questions

[9899pathfinder]

Recently got a "cylinder 2 misfire" on my '03 QX4. I replaced the coil pack but soon thereafter got the same code for #5 cylinder. 2 questions:
1) Is this typical; ie, do the packs usually fail at around the same time? In my case, about 80K since the last packs were installed.
2)I tested the primary & secondary resistance on the failed #2. Primary gave a result which I believe was in spec but secondary test revealed no resistance. That obviously could explain it's failure. But after resetting with an OBD II, the QX4 ran ok intermittently. Soon, however, I got a "Service Engine" light and the car ran rough so eventually I replaced the pack. Question is, why would the engine return to running normal, even for a brief time, if the secondary had no resistance at all?

[VStar650CL]

1) Is this typical; ie, do the packs usually fail at around the same time? In my case, about 80K since the last packs were installed.

Old age happens, but the vast majority of the time, coils that fail in groups are from poor engine grounds.

[D-Rock81]

Question is, why would the engine return to running normal, even for a brief time, if the secondary had no resistance at all?

Heat soak. The best way to check coils imo is with an oscilloscope. Heat and load are important factors when dealing with failing coils. A multimeter test is not a definitive
test for a bad coil.