I like the "half your age plus seven" rule. It's very concrete. Among other questions, it answers the age-old dilemma of "how old do you have to be to start dating?": fourteen. You can start dating at fourteen, and then only other fourteen-year-olds.

Jamie, at twenty-two, can go as young as eighteen and as old as thirty. Gina, at thirty-one, can go as young as twenty-two-point-five and as old as forty-eight. Ellen's psychiatrist character Vera Washington, at one hundred and twenty-seven years old, could go as young as seventy and a half and as old as two-forty.

Of course, there isn't much dating in Florenovia. For that matter, even if there were, I imagine that in a world where "adulthood" is determined by the acquisition of licenses, where aging is cured and death is optional, there would be much less focus on age and generations. If there were dating and romance in Florenovia, there likely wouldn't be any stigma around Vera robbing the cradle and hooking up with a sixty-year-old.

Of course, like all nice neat concrete rules about human behaviour, the "half your age plus seven" rule is, tragically, a big ol' pile of bullshit. There are plenty of fourteen-year-olds who are absolutely not ready to date, and plenty of successful May-December romances (for whatever definition of "success" you would care to use).