For some writers, querying their work and finding an agent or publisher is a quick and easy process. If you sent out twenty or fewer queries before getting your agent, congratulations, this post is not for you. But the majority of us spend quite some time in the "query trenches."
Querying can be hard work. I don't want to imagine how stuffed with queries a popular agent's inbox might be. But your outbox can be just as full of sent queries. Keeping track of who you've queried and what has been requested and sent can be a full time job.