Science is on it!
In fruit bats, anyway. Look. Science made you a chart. Here is the chart science made:
Research from the university of Exeter has has found that, in a study of fruit bats:
Males never withdrew their penis when it was licked by the mating partner. A positive relationship exists between the length of time that the female licked the male’s penis during copulation and the duration of copulation. Furthermore, mating pairs spent significantly more time in copulation if the female licked her mate’s penis than if fellatio was absent.
People get grants for this stuff.
So the next time you’re feeling sexually giving, tell your boyfriend that you want to do it like they do on the Discovery Channel when the Discovery Channel is showing a very special fruit bat episode. - PLoS ONE via I Love Charts