Before you have a fire! I hope you don't ever have a fire but I believe it's a when and not if, unless your clean, clean,clean.
Clean the roaster itself and chaf out daily. I give the ducts and chaf cyclone a monthly cleaning. Every other month I do the vertical exterior chimney too. I made a flexible brush extension to do it from the ground now.
Every 6 months or so I get out the chisels and scrapers to REALLY clean the fan and pipe between my roaster and cyclone.
If I notice I am adjusting my roasting profiles fan speed too much it's time to clean.
A 13 year old with small hands helps get into the tight spots too!