There is no evidence that a short abstinence increases the health of sperm. The volume of ejaculate has little relevance to fertility. The World Health Organisation guidelines consider anything of 2ml or greater to be totally normal, so a teaspoonful is perfectly OK. The volume reduces as we get older, and also if you ejaculate frequently, but this does not effect your ability to father a child. On the contrary, there is evidence that long periods without ejaculation, for example after a long-term illness, might reduce the quality of the ejaculate rather than increase it.