I just paid my furnace guys son to clean out my dryer duct, about a 25’ horizontal run I installed in about 1977 when i relocated the laundry to a raised area, leven with the home, so a slight downhill slope. Had never been seriously cleaned, only the visible at the dryer door/filter… I was surprised at how much he was able to get out of there, using the dryer’s blower, while he snaked in a widget to clean the walls… Originally I had flex duct, but it caused back pressure that tripped heat sensors in the old dryer, so smoot aluminum piping solved that, so many years ago!
So once in 50+ years, $100 was well spent…