How long does it usually take for an app to get included?

I see lots of merge requests that seem to fulfill all requirements but don’t have the review-requested label or any comments by maintainers. I’m not familiar with the F-droid process, and I don’t want to put pressure on volunteer maintainers so excuse my ignorance. Google Play takes less than a day to publish usually, so F-droid is not really optimal if there’s an urgent need to deliver an app to people, is it?

It depends on volunteers time to process the app (build, run, offer feedback)

Your observation is correct. One can easily wait for a month or more just to have the app included. Then, for each update, expect between a week or two. People are nice and help a lot, it just takes a lot of time and energy.