Boldjava is right on the money. The heater and the fan are the 2 items that require maintenance. Heaters seem to be better now. I used to replace them every year. My last one has been in 3 yrs with many back to back sessions. Now seeing that I cannot reach the max temp 482 so time to replace. I keep a spare on that. The other issue is the fan which the blades will become caked with fine dust and the capacity will be dramatically reduced hence the vacuum suggestion. You could take a strong flashlight to see how much build up.
While your in dealing with the heating element you can take the fan out and blow off the blades. Eventually the fan needs to be replaced as mine does now. I'm seeing chaff not making it out of the glass chamber. This will be my 3rd fan and maybe 5th heating element over about 10 years. Great unit but heat is not kind to it.