This is the reason you see the same guys in porn over and over an over. Only about 20% find that they can even achieve an erection once they realize they are inside a fishbowl.
We've been down this road. My advice is:
A. Clear the set of ANYONE not actually involved in production. EG - no one gets to sit around and just watch.
B. Keep things quiet. We used to tell people if they joked or talked during a sex scene, they were gone.
C. Watch the temperature. Sounds strange, I know, but those lights get hot. When we figured out ways to cool things down a little (without getting cold - the other bad extreme) we noticed a substantial difference in performance.
D. Try and do as much of your direction before the camera goes on as you can. The biggest bug bear in shooting long scenes for most is the stop and start aspect. Particularly stills. Stills were always the worst. You have to stop, and pull out a little so you can see the penetration, and then hold it. Nothing quite as unsexy as that - though you gotta do it.
E. Drugs and booze off the set, period. Some talent will tell you that it helps them, 'takes the edge off', etc. Our consistent experience was just the opposite. The most aggravating shoots we ever had (men and women) came with talent that had smoked up a little before shooting.
F. Fluffers, fluffers, fluffers. Man, will you save some time with a good fluffer. And she needs to be good, eg, more important than being super-hot. A hot looking fluffer who gives bad blowjobs is simply a waste of money.
G. The most important - when you find a guy who can keep it up, use him as much as possible. They are rare.
The bottom line is - it's always hard to find guys who can do it in front of the camera in a consistent fashion. Particularly when so many guys are convinced that they would love to do it.
