In my experience, most women become more sensual and stimulated around age 40 when they begin shedding the roles society dictated for them (ingenue, supportive wife, doting mother, career woman) and begin truly embracing their sexuality.
Speaking for the males, I could be emotionally and mentally stimulated up to when I started hormone therapy for prostate cancer and became basically androgynous in my 80's, although I needed a little help from pills or injections to get fully up to the challenge physically beginning in the 50's.