Do they have to make it once a night in order to use Flurry of Blows, or once a week, or what? I 'legitimately acquired' a PDF with 'related material'.
Heading: Sex and Humor.
There is a whole section on the duration of a sex act and ways to prolong it.
However, "Nymphology," from Mongoose press.
They range from the ridiculous Ale Goggles.