Middle-aged parent names? What works and what doesn’t?

[name_m]Just[/name_m] wondering here, with many people obsessed with calling names old or middle-aged, what goes along those lines and give me from different birth periods like the 1910s, 1950s, 1970s, etc. For all that you mention, what works and what doesn’t?

On this website people have talked about the 100 year rule, which means a name that was common in 1918 should be ready for a revival in 2018. That doesn’t apply to names that are timeless and have always been popular and still are, like [name_f]Elizabeth[/name_f] for example.
[name_f]Susan[/name_f], [name_f]Karen[/name_f], [name_u]Kimberly[/name_u], [name_m]Steven[/name_m], [name_m]Timothy[/name_m], [name_f]Cynthia[/name_f] etc all were popular in the 60’s so they aren’t ready for a revival.
On the other hand, [name_f]Florence[/name_f], [name_f]Annie[/name_f], [name_f]Ruth[/name_f], [name_f]Margaret[/name_f], [name_m]Albert[/name_m], [name_f]Mabel[/name_f] etc AKA names that were popular in the 1900’s are being revived.
The rule doesn’t apply to all names though, some names from the 1900’s like [name_f]Bertha[/name_f] are still considered very dated (though maybe it has to do with the fact that [name_f]Bertha[/name_f] stayed in the top 100 till the 1930’s)