I have some information regarding this:
I am not familiar with Bioenergy, but ejaculation does decrease qi. It is important to regulate your sexual activities, especially men over 40. Everybody is different regarding this. It is a matter of saving and spending energy. Some common symptoms of overspending are chronic lower back pain, pain at your kidney level on the back, pain at your sacrum, low energy, dizziness, or ringing in the ears...
Also, here is some info on erections:
"In a healthy individual, the body wil have biological signs indicatin the rising of yang energy. In men, this is indicated by the stiffening of the sexual organ at the end of extreme yin energy and beginning of rising yang energy. When an erection occurs naturally in a healthy male without sexual thoughts, it is known as the biological midnight of a person. The best time to practice Microcosmic Circulation Qigong (small universe)is during your biological midnight." I got this quote from the book Qigong Empowerment, by Master Shou-Yu Liang.