Some people I know who did a lot of that while growing up had zero staying power when they needed it most.
I believe I read somewhere that most people train their bodies to finish quickly when they are masturbating, sometimes because they must function quickly to prevent someone from finding them in the act. Another cause may be that, since they have no one else to please, people commonly just get to the good part as quickly as possible. The men I know who had this problem found it to be a big handicap in their relationships, sometimes a fatal handicap, and sometimes it took some time to improve the situation.