Testosterone plays a key role in a man’s sexual experience. Testosterone levels peak in the late teens and then decline. Most men notice a change in their sexual response by age 60 to 65. The penis may take longer to become erect, and erections may not be as firm. It takes longer to reach full arousal and have an ejaculatory experience. As a man ages erectile dysfunction also becomes more common. Medications are available for erectile dysfunction, speak to your doctor.