Remember to contact a Doctor if you have an erection lasting more than four hours. 
S-h-i-t, I'd be calling everyone I know to boast about it if I did - I'd probably even rent a skywritng plane to let the whole city know too...
Clever marketing by those ED companies.
As a producer/director I can't recommend ED drugs for a performer (in case they go blind or keel over with a heart attack), however I suspect that many stunt cocks do use such drugs. As I understand it, in the old days some of the guys used to do syringe injections into their dick in order to perform...YIKES!!!
As for me, I rarely get an erection during a shoot (too many technical details to pay attention to), but I'm good to go au natural in my private life, since I have a pretty strong sexual libido.
ADG