Another good reason for safewords, even if partners know each other well, is that in the case of females many things, hormonal and emotional may affect what their limits may be at a particular time. At certain points in her menstrual cycle, a woman may be more or less sensitive to pain. If anyone is not well rested or hungry or tired they may not be able to take as much as they have previously.

We always know my safewords are there, even though i haven't used them in years.