As I say, it's possible to set up a whole bunch of tags right away. And from my poking around things like kink_bingo, it's possible for posters to ask for tags to be created so they can then edit their posts to add the tags.

And right at the beginning is when most tags will need to be set up. After that, you only need to add one or two at a time - and that's not necessarily even once a week.

(And it's always possible to add a co-maintainer to help out.)