How long does it take for today's violent wildfires to go out?

When a massive wildfire erupts in the United States today, it can leap over formidable rivers, produce whirling tornados of flame, and cause tens of thousands of people to flee. 
These modern infernos — enhanced by a warming climate that makes for profoundly parched land — are burning over twice as much land than they were in the early 1980s, breaking all-time records. 
After flames spread over tens or hundreds of thousands of acres, it can take quite a bit of time for the