I've gone through 3 over the range microwaves in 3 years.
"shadowcat_378 popping and sparking could most certainly be a sign of a cracked magnet and the only viable repair would be to replace the magnetron. Here is the thing so, there are some pretty powerful capacitors on the inside of your microwave. If those do not get properly discharged they will pack a punch. We are talking lights-out punch here! So if you are not quite sure you want to fix your microwave by yourself, don't!
If you can give us your exact model, we may find some more instructions for the repair of it.
Do microwaves have a life expectancy before they go kaput? Yes, but 1 to 2 years is definitely not it.
Could moisture be getting into the magnetron causing it to short out? No, you'd be looking at other components that would fail first.
Is it a requirement to run the exhaust fan on the microwave when cooking on my stove? No it is not. Strictly an exhaust fan and not related to the fan on the inside of your microwave.
The only suggestion I have is that you consider getting a well known reliable brand (Farberware, GE and Panasonic to a lesser extend) or go all out and get a commercial microwave ."
"According to Mr. Appliance the average lifespan is 8 years
LOW HIGH AVERAGE
Microwaves 5 10 8"
I discovered that it’s the way it’s being cleaned. After 4 microwaves I discovered it’s because when it’s being cleaned they spray the cleaner into the microwave. This causes it to short. You must put cleaner on rag then wipe.