I know a case which happened a few years ago in a company where the cargo fire warning came on during cruise, the fire extinguisher was triggered and the warning did not disappear. The crew continued to their destination because it was the closest airport anyway. A full evacuation was done and after the cargo door was opened...big surprise...false warning!
When you are not able to determine if the fire is out it sometimes seems to mee you can do whatever you want do you will have to talk to your chiefpilot afterwards anyway..... Especially in the mentioned case above where the airplane was a turboprop. No slides are installed and people have to jump out and can get hurt. Using the stairs could be a good choice but in case the fire is still on the crew would be blamed in the incident report to have acted in a reckless way. So for safety reason it is always reasonable to perform a full evacuation procedure.