15.5 no spark issue time after time.

I have a 2000 craftsman mower with a 15.5 Kohler engine. The issue is after it sits for a few months I get no spark, no start. every time I cleaned the rust off the flywheel magnets and replaced the coil. It runs fine. I'm on my third coil and again no spark. The last time it seemed the flywheel/magneto magnets were very weak, Do these go bad and lose their power? Sometimes it mat sit for 7-8 months and that's when it seems to act up.

Rust on the coil or magnets make absolutely no difference to the generation of the spark.
Magnets go weaker over time and this proces is accelerated by heat and mechanical damage as would hapen if it was striking the coil and not passing .010" to .020" away.
Unless you have it sitting somewhere that is subject to very strong magnetic feilds like a large DC welder, the magnets will not go off is a single season.

What test exactly did you do to determine that the coils were bad ?

when I changed the first coil and had it in place the magnet sucked it in with a strong force. I clearance it and tightened the coil in place. It started right up. 4-5 years later same thing, no start. No spark even with a small screwdriver inserted in the boot holding it near ground. 2nd coil started right up and ran perfect, Fast forward 5 years later, No Spark. I ordered another coil and installed it, this time it hardly had much magnetic pull. .020 wouldn't fire. I set it as close as possible without the flywheel striking it and it started. I shut it down after mowing and 2 weeks later dead again. I am a mechanic of 40 years and have rebuilt more engines and worked on cars from the 30's to 2010. I get how this stuff works but this is pissing me off. Thanks for replying and maybe I've missed something, I just hope you or someone has had this issue and have a cure.

Are you isolating the coil from the mower to ensure it is the coil and not one of the safety switches ?

There is only 1 wire that hooks to the coil. I assume it must be a ground to kill the spark when you shut it down. Duh, that's the only thing I haven't done was to disconnect it and try to start it. If I'm not mistaken, the only safety switch that kills the engine is on the seat and I jumped that wire to bypass that because every time I hit a big bump or raised up to see over the front it would shut down. I appreciate your input and I will fiddle with it some more and let you know what happens. Thanks.

You disconnect that wire for the purpose of checking the coil and that is the only reason.
All of the various kill wires come together to a common wire then go to that wire, including the stop wire from the ignition switch.
I never ever tell people how to dissable safety switches on a publicly accessiable forum because it stays on the web forever.
All of the ignition safety switches will be normally open so follow the black wire and check the switches.
One of them is faulty or somewhere the kill wire insulation has broken down and it it shorting to the frame.

You should be able to get a wiring diagram for your mower off the Sears web site.
If you have trouble understnding it ( like 90% of the rest of the population) post the diagram here and we will walk you through it.

weary, shorts to ground on old wiring difficult to detect. try jumping some new wiring if possible. also use the wiggle test while running