I have noticed the same. I am adding it to the action list for the whole Challenge checker project that will get most/all attention the coming weeks.
A fix has been made in the development environment now. Time reduced from 45 seconds to 1-2 seconds.
There was a bug when creating new tags that it reindexed ALL tags for full text searching. It was only supposed to index the new tag of course.
Editing tags used the same code, but in that case it worked fine.