There are exceptions, of course, but chlamydia is rare in women over 25 and men over 30 years
of age; gonorrhea occurs
in somewhat older folks, but also is very rare
in both men and women over 30-35. And syphilis is virtually nonexistant outside certain restricted populations, including gay/bi men and certain ethnic groups -- e.g. pockets of First Nations Canadians, African Americans in the south and urban areas of the US, Latinos (especially illegal immigrants) in the southwest.