In adult videos, the guy is being sucked for five minutes, then he puts his cock in the woman and they go at for ten minutes and when it is time for the money shot, it takes the guy five minutes jacking off before he cums. In real life, the average guy would have exploded during the time the woman was going down on him. 
Veteran porn star Peter North says staying hard is a challenge that most male porn stars will confront at some point in their career. "Everyone thinks it would be so easy to stay hard on set and it’s not easy at all," he says.
While we'd all like to believe that the ability to stay erect for hours at a time, that's not always the case, says porn star Kayden Kross. “Most of our male talent uses some form of medical aid to stay hard,” says Kayden Kross. “That can be anything from Viagra and Cialis to injections that will keep erections going without arousal. I know others have had surgeries to implant penis pumps.”
Kross says that often, her coworkers will pop a pill before any scene they shoot to achieve an erection and go on their merry way. But it's usually obvious when this is the case.
“Sometimes with the pills they'll look a little flushed, but sometimes you're just flushed because sex is an aerobic activity,” says Kross. “With the more hardcore methods (injections, pumps), you can tell because the dick doesn't respond to situations where arousal would naturally dip. For example, one guy once fell through a glass wall on a shower in the middle of a scene. He stood up with shards of glass sticking out of him and his dick was still hard. Viagra is strong, but it's not that strong.”
Male Porn Stars Share Their Secrets For Staying Hard on Set