Officially, this is called Premature Ejaculation (PE), and it’s a problem for us making shoots like this – not to mention for the couple themselves. As for ED (above), if this is a chronic problem for you there are some good solutions out there to help – speak to your doctor – don’t be shy, you deserve an awesome sex life!
During the shoot, it’s absolutely no problem to slow it down or pause entirely to reduce stimulation, but being conscious of when you’re close to the point-of-no-return is necessary for this to work. Might need some practise (tough job).
Depending on your refractory period (how long after an orgasm til you can get an erection again), a break may be all that’s necessary, and you’ll be somewhat desensitised as well so the next session you may be able to hold it for longer.
But, typically we’d just work on some other activities that do not require an erect penis (there’s plenty!), and re-try the erect-penis stuff later in the day. Or, we could stop the shoot there, and try again on the the video day tomorrow (shoot stills in the morning). That can get tricky, but Shoot Producers can be flexible like this usually.