Likely not a plug problem. Our saws don't really get put up for winter as that is when most fence lines and road banks are cleared. I do have saws that set for 2-4 months without being run that will start with a few pulls. I do have for Huskies.
Here is what I do and it seems to work. I used sta-bil gas treatment in all my small engines including those that run on mixed gas. I only use NKG plugs on 2 stroke equipment.
If you are setting your saw up for several months empty the fuel tank and run the carb dry before storing the unit. I think you are dealing with a problem resulting from the gas evaporating and leaving the oil in the carb, when the "new" gas enters the carb in the spring you have an oil rickh mix that fouls the plug.
The above has worked for me for about 14 years without fail, your mileage may vary.
