Randomly it happens. As for sloppy seconds:
Whether it feels better to the husband or wife is debatable but I know that I take an exquisite pleasure from it and so, too, does Michael. Part of it is the physical sensation of the penis moving in a vagina that is loaded with semen, part of it is the emotional impact of your man stirring up another man’s sperm as he takes his pleasure inside of you.
http://www.amazon.com/Cuckolding-pat.../dp/1480097349