Kohler Magnum Coil Failing/Weak?

[Trent]

Well, I got things set up today and made 2 cuts. Shut the engine off to do some other work, when I came back she would not hit a lick. Checked the fire and sure enough, it was dead. Disconnected the kill wire, still no fire. A couple hrs. later I was writing down the model # and decided to clean the magnet on the flywheel, and clean the laminated steel on the coil. Well what do you know.. runs like new again. The engine is about 17 years old and I don't know if cleaning it helped or did the coil cooling down make a difference. There are no other parts involved (no electronics, no points) that I can see. Would this coil go bad over time, or all at once? I'm scared to price a new one. 
Man that board I cut looks good! Thanks 

[ladylake]

Trent   Coils most of the time act up after getting hot. Just keep running it, if it quits again with no spark most likely a bad coil. I wouldn't think the price would be to bad.   Steve

[olyman]

also--and i dont know why--but the rust buildup you cleaned off the laminations---will creep under the mounting posts---hence--no contact---hence---no spark---been there---have to have a good ground for the coil to work-----