Psychologically this might be a tough question, but in means of biology, what are the effects of total celibacy on the gonads and the nervous system concerning both man and woman in short and long term? Has there any research made in medical terms and as a bonus question, is there anything similar on other animal kingdom like deliberate celibacy?
I was told in my undergraduate degree that males produce sperm all the time, and that under conditions of no sexual stimulation, that sperm is excreted involuntarily every 15-16 days, at night, while dreaming. I was also told that the renewal rate of sperm is higher under regular sexual stimulation, which increases the fertility of the sperm that is excreted.
Not entirely on your question but I think sufficiently relevant:
This paper (freely available) identified a non-causal link between ejaculatory frequency and incidence of prostate cancer.
Men were asked their age at first ejaculation, the maximum number of ejaculations ever experienced in 24 h, and to estimate the average number of times that they had ejaculated per week in their most sexually active year in each of three decades of age (i.e. third, fourth and fifth).
Leading to results indicating that:
Greater ejaculatory frequency in the most sexually active year in each of the three decades was associated with a significantly lower risk, with men in the upper quartile of ejaculatory frequency having about two-thirds the risk of those in the lower quartile for the third and fourth decade, and four-fifths the risk for the fifth. Ejaculatory frequencies in each of the decades were correlated with one another (r = 0.5–0.7). A similar finding related to the total number of ejaculations over the three decades. Those who reported an average of four to five or more ejaculations per week had two-thirds the risk compared with those who, on average, ejaculated less than three times per week.
Giles, G.G., Severi, G., English, D.R., McCredie, M.R.E., Borland, R., Boyle, P. and Hopper, J.L. (2003), Sexual factors and prostate cancer. BJU International, 92: 211–216. doi: 10.1046/j.1464-410X.2003.04319.x