He cums at 13:54. From the looks of things, they had to film the entire scene after the poor guy pops. Since they're using so much natural light, they're also in a hurry to get things recorded so it doesn't look too strange to the viewer. It's also worth noting that steroid use (and particularly HGH use - most lump "steroids" into any type of PED) actually increases libido. Decreased sex drive from steroids normally only occurs when someone is off cycle and has inhibited their own test production due to abuse.