Not a rule, but a suggestion about "Boys"
I, and most people have no sexual interest in "boys", but I wind up downloading movies labeled as containing "boys" because the movie producers consider men in their 30's to be "boys"! Here's a suggestion, call males over the age of 18 "young men" instead of "boys".
Of course people mature sexually at different ages, but I can't recall ever seeing a sexually mature male under the age of 16. That happened unknowingly when a 16 year old who appeared to be older than that was lying about their age and doing porn at 16. Two cases like that were BelAmi's Oliver Krist and Cobra's Brent Corrigan. What I like to see are males at their peak of sexuality and fitness - which seems to be from 19 to 24. Pedos such as Jared Fogle make me sick. Jared is famous for saying "the YOUNGER the BETTER". Jared liked to watch hidden camera footage of naked 9 year old boys changing their clothes, and even then, he wanted them younger!