At what point in size does it become unusable to select from a taxonomy list for an end user. I have a UI, used by the persona of John Q Web User, a user with no particular tech savvy who expects the UI to be fairly intuitive. This is not some admin or super user. When presenting this user with a list of taxonomy terms, in the form of cards, at what point does the number of terms become difficult to manage?
Our taxonomy today is too broad at 9 terms, but I am concerned that it will be too granular and difficult to navigate at 30 terms. Is there any research indicating a sweet spot that you know about?