This is way off topic for the Computer Chips section, I'm afraid................................
When we have the time, after taking care of our paying customers, the people that actually keep us in business - *then* I can think about trying to steal a few minutes to answer questions that are appropriate/related to the topic of this section - that's about as far as it goes here, my friend.
I agree, you raise an interesting question as to the actual deterioration of coil packs - and in our experience it varies - from one batch to the next sometimes, as well as based on what year of vehicle, the actual style of ignition coil, etc.
I really am not qualified to argue Tesla's work - but I do not believe one can use his work as "proof" that automotive ignition coils absolutely cannot and do not deteriorate - what we have seen does not bear that out.
Ever tried doing any hands-on measuring/testing of the actual output of these coil packs brand new (which isn't "good" to begin with), and then again after say, 3-4 years and 50K or 70K miles? Ever tested their saturation times/capability when brand new and again after some time/miles, etc?
We've done a bit of that over the years in our work with various ignition manufacturers, and I'd be the first to say that this is one area where I'd like to be able to spend a *lot* more time and R&D. In fact, it looks like we're going to be releasing a new COP ignition upgrade in the next few months (though it's going to be expensive, something really only appropriate for racers or those with $$$ to spare, etc.).
Automotive coil packs like modern FoMoCo units have to function in everything from 60 below 0 (F) to 220 above under the hood - dry to soaking wet, liquid to ice - constant shock & vibration any time the vehicle is being operated, with COP units mounted recessed in a well where they are constantly being "cooked," using raw materials sourced from the lowest bidder, being "pushed" by the PCM as the coil packs, plug wires & spark plugs on the older pre-COP ignitions age, etc. - especially the spark plug wires on the 1997-1999 4.6 F-150's, for example.
Their output and saturation times do not always remain a set constant over time. They vary - some deteriorate significantly while others deteriorate very little, just as you might imagine - and this is usually related to the coil design and it's direct proximity to heat (and just how much), vibration, contaminants, etc.
I replace the COP coil packs in my 2001 Lightning at least twice a year - and immediately see improved idle quality & throttle response as a result. Depending on how long I leave them in, we'll also see a bit more power & fuel mileage - some of the changes (particularly mpg when changing 4 month old coil packs) are small enough that it would really take truly repeatable lab conditions to identify/quantify properly.
Overall, with as long as most owners keep the stock ignition components in these Ford trucks & SUV's, there's easily enough difference there for us to see noticeable improvements in 1/4 mile times, throttle response & fuel mileage, for example, just from replacing the coil packs alone.
You might want to try talking with companies like MSD, Accel, etc. - the actual manufacturers of high-performance ignition components, and see what they have to say - assuming you can actually get a real engineer on the phone who is willing to take the time, and second, actually share some meaningful data - but it's worth a phone call just to get up to speed on their view of "the basics."