Surveys have showed that around 50% of people, as they age, reduce the number of sexual inhibitions -- that means less worrying about sex and more enjoying sex. Meanwhile, around 25% of people aged 50 and over say that their sex life has been improving as they age.
Part of the reason that things improve may simply be time. Kids are grown, retirement is in sight and most stressful life decisions have been made. Other reasons could include living with a long-term partner and an acceptance of one's own body.
The main complaints of people related to sex as they age is more physiological. Older people have to plan more for sex and may need aides to counter aging-related sexual problems like erectile dysfunction.