Once a year for most households. Large families, pet owners, and homes with long or roof-terminated vent runs benefit from every 6-9 months. If clothes already take multiple cycles, do not wait for the calendar.
The lint screen catches only part of the lint - the rest travels into the vent line and accumulates there for years. The screen is daily maintenance; the vent line is what we clean.
Usually under an hour, including an airflow check at the termination. Combined with air duct cleaning it adds little time to the same visit.
Yes - commercial dryer runs clog faster than residential ones and carry the same fire risk. We service multi-unit and commercial laundry vents across the metro.