Slower drying and a hotter smell are exactly the signs I would take seriously. My dryer did the same thing with towels: first they needed a little extra time, then the laundry area started feeling warmer after each cycle. I cleaned the lint trap, but the problem stayed, so I checked https://dryerventcleaningtoday.ca/advice-for-homeowners-on-dryer-went-maintenance-safety-and-cleaning/ to understand basic dryer vent maintenance and safety. It reminded me that lint can build up beyond the screen, especially inside the duct. After the vent was cleaned, the hot smell stopped and clothes dried normally again. I would not wait for a full failure. Small changes in drying time are often enough reason to check airflow.
If clothes dry slower and the dryer smells hotter, checking the vent is reasonable. It may be something simple, but airflow problems can get worse with time. Cleaning the lint screen is a start, but the duct and outside exit matter too.
Last week my dryer left hoodies slightly damp, and the next load had a warmer smell than usual. Nothing looked broken, so I almost ignored it. Still, it made me wonder if dryer vent maintenance should start as soon as clothes dry slower or the machine smells hotter.