Quoted from mbaumle:The Walking Dead is an enormously popular show currently, thus making it a valuable theme, but extended popularity will be questionable when the show ends
Debatable- the whole zombie genre might be on the tail end of popularity but it's still a huge part of pop culture from the mid-aughts onward. You can say it predates that, but there's been a big bubble in zombies and apocalyptic and post-apocalyptic everything since 06 or so.
I personally have very little connection to the super-patriotic bicentennial pins of the mid 70s, but love that they embody the spirit of the times.