Yeah, sounds like your ends just broke. I doubt that was caused by the coil, though; more likely it was the other way around. Working into an open circuit like that puts extra stress on the coil, rotor, cap, etc.
In fact, a buddy had his brand-new rotor fail completely on the way home from VTR 2000 in Oregon. Rotor looked brand new, we never could really find the carbon track that had to go through the center of it, but replacing the rotor was what fixed the problem. When I checked the plug caps, one of them was completely open (and in fact fell apart when I tugged gently on the wire). I stripped back the end of the wire and attached it directly to the plug (by using the threaded sleeve as a nut), which got him the rest of the way home (some 700 miles).
Too soon to say how long they will last, but I've been trying some NGK caps that are normally sold for motorcycles. I figure that if they can survive the rigors of being exposed to the elements on a motorcycle, they should be able to handle the environment under a TR hood. I got ones with a 120 degree angle in them, to reduce the stress on the wires. Don't recall offhand where I got them or what the part number was, but these look like the same ones:
https://www.rockymountainatvmc.com/...NGK-Universal-Spark-Plug-Cap-120-Degree-Elbow
It would be kind of fun to grind off the NGK logo and paint on a Lucas, but I haven't bothered. Yet.