Woman have played 5 sets in the past in the WTA finals, and were due to at one of the Aus opens, but due to lack of consultation that never panned out.
Women voted previously to play best of 5 but no tournament was interested. Being better at endurance events than men (usually ultra endurance though), there shouldn't be much of a problem with energy levels.
One issue could be injuries. Women generally suffer from more injuries than men, especially knee injuries due to wide hips creating more of an angle where the femur joins the knee, but also more soft tissue injuries. I wouldn't really want to see retirements.
It's also worth pointing out, that the ATP (men's) tour doesn't play best of 5. Only the ITF Grand Slams play best of 5 for men. So at pretty much every other tournament, men and women are both playing best of 3.