There are a number articles about penile blood flow on the Internet. Superficial vein pages can be found with this Google search:
http://www.goog … ?q=penile+veins
Add “corpora” (for corpora cavernosa - CC) to that and you’ll (generally) get information about the deeper veins:
http://www.goog le.com/search?q … e+veins+corpora
Here’s a nice summary of venous draining: . It explains how there are two dorsal veins. The deep dorsal vein drains the blood from the corpora cavernosa and the superficial dorsal vein drains the penile skin, glans and corpus spongiosum. It also explains the pathway that blood takes to exit the penis.
An erection is maintained when the subtunical and emissary veins are compressed by the tunica albuginea that has expanded due to the inflow of blood into the CC. I suppose it varies from man to man how well an erection is maintained based on how “sensitive” his emissary veins (which pass through the tunica) are to being compressed.
There’s a nice image of how that works on this page: http://www.whit … om/Erection.htm
To answer your questions: A large superficial dorsal vein might drain the glans faster, but wouldn’t affect CC drainage. The number and size of your emissary veins would probably be the determining factor in how fast you lose your erections.
As long as you can get it up again and maintain an erection with chemical or neurological stimulation and can still function sexually then I’d say you’re doing the best you can with your individual anatomical assets.