Men peak sexually in late teens & early 20's. During intercourse, they reach {orgasm} rapidly, {ejaculate} powerfully & are able to have another {erection} quickly. As a man gets older, more stimulation may be necessary to achieve erection (which may not be as stiff as in the past), & ejaculation may be delayed. A 2nd erection may take longer.
However, there is absolutely no reason why both sexes shouldn't enjoy a healthy sex life well into old age. In fact, many people find sexual activity becomes more enjoyable with increased experience & confidence. If you have problems, discuss your feelings with your partner & experiment with different forms of sexual contact (e.g. mutual stimulation, {oral sex}).
