Hello, I would like to share some thoughts on this, after reading a lot of books by Marc 'the animal Macyoung and others.
Most of the experts say only seconds because the person who throws the first blows will continune hitting the other person who was not expecting a abarge of blast. The adrenline will kick and in and you will be exhaust very fast, natural way of giving us a fight or flee response.
It seems most fight are very short. High School kids up to College kids than to fight more boxing style because of the way they see peope fight. There fights will last a little longer because of the exchange of punches only.
Street fighter/Bullies know how to destroy you and these fights will last for seconds. From chairs to bottles,kicks,head butts, and all the other stuffs for NO Rules with anything goes....More combat style for survival.
Everyfight will be different and no such thing as a fair fight! It seems the key is to end the fight as quickly as possible and make sure the other person cannot fight back when it is over? No one wants to go to Jail so know you laws and when to run away.
Learn to avoid, descalate and leave....watch your EGO and don't let it make you do dump things like trying to be tough back! We only have one life and you may want to grow older?