Measure the symptom, not just the runtime
Notice whether the vents have strong airflow and whether that air feels meaningfully cooler than the room. Also note whether the outdoor equipment is operating.
Rule out simple load and airflow issues
Check accessible filters and blocked vents, and make sure doors and windows are closed. Extreme indoor heat gain can affect recovery, but persistent failure to cool still needs diagnosis.
Call when performance is clearly abnormal
If the system cannot maintain temperature or runs for long periods without normal cooling, schedule AC service rather than forcing the equipment to keep operating.
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.