It's stressful, you know.
You're only limited to a certain amount of time and you have to come before that limit....it's not chicken feet lor....before that, if it's a new actress, you got to put her at ease also....not so easy....
Also, there are such things like fake penetration(when got mosiac etc) and acting along with those actress....then, use stuff like shampoo to substitute....
Lastly, you may be tempted to want to "enjoy" more the figure of the actress but you're restricted by what the director wants and as mentioned, time constraints....
Forgot one thing, don't you think you'll get sick of doing it as you are called to do so.....? Even if your mind is not tired, physically, your bro cannot take it also.....

Every job have its pros but also cons as well.
