We have a 60 day cycle where we remove individual routing negatives and negatives for paused exact temporarily to check if they are still generating queries we need to block. If the queries return, we add the negatives back within 24 hours if they go over a threshold.
We do this because there is a limit on the number of keywords in a shared library and a limit on the number of shared libraries you can have. It's often the case that the number of paused exact keywords is larger than the limit on the number of keywords in a shared library. To work within this limitation we prioritise by spend, adding the highest spending paused queries or misrouting queries to the list.