An interesting post about why we should ejaculate at least 1 day a week:
"It gets quite complicated but within certain tissues of the body there are androgen receptors. When an angrogen hormone (dihydrotestosterone) attaches to the receptor it signals instructions to be carried out from within the genes of target cells. DHT is the essential key hormone for sexual health and penis growth and maintainance. Sexual stimulation causes the activation of 5 alpha reductase to convert testosterone into DHT within the penis tissues. More sexual stimulation causes more DHT conversion, because your sex organs need DHT to function at prime. Ever hear of the saying "use it or lose it"? It applies quite well to the penis and associated sexual anatomy. Without sexual stimulation (ever wonder why it's called sexual chemistry) your body drops its conversion of test to DHT, which results in diminished sexual function and developement.
Gentle manual exercise performed while highly sexual aroused will cause a rapid conversion of testosterone to dihydrotestosterone within the genitals, both external and internal." -
The hormones you need to know - Page 2 - Matters of Size :: Free Penis Enlargement Forums and Exercises