Absolutely when a cigar has gotten bitter or hot.
I first tried that when I was out of matches and my stick started to go out ... it totally works!Btw, I see a lot of guys saying they do it when it's too hot. If you blow for more then a second or 2 it actually increases the burn/heat a lot.
A guy posted a great blog elsewhere a while back explaining this topic. One of his comments was how he uses long purges to heat the cigar to fix a uneven burn. When I try that it works about 75% of the time.
Try massaging the caps end. Sometimes the heat and moisture simply swelled the tobacco.It helps me get a better draw on a tight cigar.