Safety changes the decision
Combustion or heat-exchanger concerns are different from ordinary component failures and should be handled with appropriate professional evaluation.
Recurring repairs matter
One repair does not automatically justify replacement, but repeated failures can change the long-term comparison.
Think beyond the furnace cabinet
Airflow, controls, ductwork, venting, and system compatibility can affect both repair outcomes and replacement planning.
Safety note: If you smell gas, see smoke or fire, suspect carbon monoxide, or believe there is an immediate safety danger, leave the area as appropriate and contact the relevant emergency or utility service. Do not treat an active safety emergency as a routine HVAC appointment.