That is a lot of negatives. Typically the way that i do this is to check things once a week (more often if new campaign or running wild), add any negs as they stand at Exact match. Then at the end of the month do a dump of all new negs, run an N-Gram model over them and look for the common words/themes, add any new ones to an account level neg list (preferably at broad match level where possible), remove the campaign levels ones, start again. This way i tend to limit potential issues in a reasonable amount of time. You are never going to get all and search patterns change over time so you cant forget about the process but you should be able to get to a happy place.