I've seen alot of post's about replacing COP's even when there is no problems with them??? I understand if you got a mis-fired and so on, but just to replace them at a set time. I don't think they have a duty life span ???

Wasn't the reason to have eight coils is, if one goes out you still got 7 other still working to get you home as compared to the old days when we just had one coil to strand you.

Plus since each plug has it's own coil shouldn't it last 8 times longer

 

How are they going to rob you blind if the coil lasts 800,000Miles?

 

That's a good idea, I'll do a test on how far they can go.
Right now I'm at 102K with only 698,000 miles to go

 

If its important to you that your engine run as efficiently as possible than changing the cop's should be something you should do. I have a work van with a 5.4 and I didnt replace them until they actually started to fail completely. The originals lasted to about 160K. I change the plugs in it and the cop's at the stealer ship cost $800.00 the truck I recently bought had 102K on it and it was getting bad fuel economy and it didn't seem like it had enough power so the first thing I did was do the Cops and plugs did them myself cost $300.00 I bought the motoblue that claim a 15 hp increases in power just from them. I dont know about that as I dont have a dyno but the truck does run better. Guess you could wait till they quit on you. One thing the 5.4 has that spark plug blow out problem so it would be unwise to wait to long on that engine.