When a woman asks this question with regard to men, my answer is that guys enjoy climaxes for the following reasons:
1. Pleasure
2. As an expression of the love he shares
3. Making babies
4. Stress relief

It is not unusual for a young woman to be upset and hurt that she is not the complete answer to her man's needs. Truth be told, she is with #2 & #3; however, regardless of how often a couple makes love, often stress and/or simply seeking a simple pleasure is independent of her involvement and interaction with her man. Now, having said that, the same is true for women, although to a different degree. I am told that women have different skills for coping with stress for which masturbation plays a less important roll, and therein lies the dichotomy.

Male or female, everybody's sex drive is different as is everyone's tolerence for handling stress and a desire for enjoying an orgasm for the simple pleasure of it all. How often a guy masturbates varies all over the place. Some guys might masturbate once a week or so, others every few days, some every day or two, while still others one or more times a day. Women have their own scale and I don't believe that age per se plays a part, although I do not know how age may affect this later as a senior. Age certainly plays an important roll with senior men and the frequency with which men much older than forty masturbate or make love becomes less. Perhaps Brandye can speak to this matter for women. All I am saying is that there is a wide range for what is normal and I don't think you can attach a number to anybody until much much later in life, if even then.