Should I replace my coils at any certain interval?
 

I'm planning on performing some routine tune-up work to my '93 325i, including changing the spark plugs.

My question: Is there a predetermined (or suggested) interval at which I should replace my coils? Although my car has 83,000 miles, I have no indication that any of my original coils are faulty.

However, since I'll need to remove them to replace the plugs, should I take this opportunity to replace the coils as well? Should I proactively install a new set since my car's existing coils have over 83,000 miles on them? Is the $250 investment good insurance for any future damage? (I'm especially concerned about my DME and the Conforti chip I've installed- I've heard a faulty coil can adversely affect a DME)

PS: I would just be looking to replace with stock coils - not Plasmas.

wait for 1 to go bad.
unless of course you have a flush wallet, or stock in a coil company.

Is it true, though, that even if 1 goes bad it could damage my ECM (and my Conforti chip)?

Its usually the DME that goes bad first>>replace all 6 coils & DME if one coil goes bad...but if ur not havn trouble>>let it ride

If that's true, that's exactly my concern. If one goes bad you say replace all six AND the DME. A new DME with a new Conforti chip will cost me $800 or more. I'm wondering whether spending $250 to replace 11 year old coils with 83,000 miles on them is a worthwhile preventative measure - to save me the possible cost of a new DME.

If ur DME is new>>then replacing the coils would be a good idea>>but if you have chippd the old DME and arent having any problems I wouldnt worry about it>>>because its the DME that is the problem.

why not ohm out the coils? the bentley has the spec on what you should see. if there within specs and you have had no tell tale signs of misfire or the like, i'd say save your money for something else...

I'll refer to my Bentley manual and check them out. I guess my bottom line question was this: Do coils have a shelf life - should they be changed at a certain interval like an O2 sensor?

Interval change, no. coils can die slowly, the dielectric breaks down, the insulation can break down and what you get is a degradation of performance. TEST...
After talking with an EE here, do the test with a heat gun brining the coil temp up closer to what it would be in actual usage. testing a coil cold is NOT a true test.

also"shelf life"
 

Shelf life refers to a coil thats sitting in storage...Under those conditions i.e. "NEW", they could sit there "Forever" and be OK... Its the constant temp fluctuation that will over time break down the "inards", again the dielectric, insulation and allow Moisture in and begin to create havoc.