Keyword Queries are, compared to other resources of your license (Briefing Credits, Page Credits or Export Credits), not a resource that refills itself every month. If I measure the success of a project in the long run, I will block the corresponding keyword queries as long as I use the project.
A project with 500 Keyword Queries blocks them every month. When I don't need this project anymore the 500 keyword queries will be available again.
For that reason i have to know, how many Keyword Queries I use in my different projects and how many I don't have in use yet.