[PubQ] How important and necessary is it to plug your works in progress/other genres when pitching agents?

For years, I thought I needed to query a new agent every time I wrote a new book I wanted to traditionally publish. But I see now that agents generally stick with you for your entire career.

So if this is the case, does an agent who wants to offer representation just decide based on that single specific manuscript and query letter without knowing what else the author is working on/if the genres are in their wheelhouse?

When personalizing a query letter, is it crucial to detail why the book I’m sending them AND what else is in my pipeline to further convince them to represent me for my entire career? Or just the former? If so, how long should this section of the query letter be?

I have a list of agents I plan to query in a few weeks that I believe are perfect for this current manuscript, but now it seems like I’ll have to go back to the drawing board with identifying agents who represent that genre AND the other genres I’d like to write books for in the near future. /:

I think those who have successfully queried an agent and are agented/previously been represented across multiple genres would be most helpful here in clarifying. Thank you in advance and I hope this helps others too!