I've worked mostly remotely, and in companies where management insists on having visibility into subordinates' calendars. So I've placed an awful lot of official sounding decoy meetings on my calendar right after meetings that were completely unnecessary (could easily have been an email), hut where management would certainly listen to themselves talk past the buzzer.

My department head made a point once to instruct us that, if you need it, you should schedule time on your calendar as a meeting to just be "heads down" on work.

We have a lot of meetings so he encourages we do basically whatever it takes to keep meetings timeboxed.

I once was in an incident call where one of the execs was brought in and eventually said "We have 20 people in this call who all have good salaries. It will cost $600 to just inform our customer service agents to take care of this. Let's get out of here"

Management has to push that culture downwards, and reinforce it themselves, and continually encourage it as people join and leave and teams change.

I always felt this was wholly ineffective coming from someone who wasn’t contributing or necessary to any given meeting, but it’s important to establish and hold boundaries like this.

Even more points when a participant speaks up at the very beginning, to announce, “I’ve got a hard-stop at 9:50, so I’ll need to leave at that point no matter what.” Then the responsibility for wrap-up is placed squarely on leadership.

Unfortunately I’ve also found that a poorly-run meeting won't get around to the wrap-up on time, and so leaving early may only hurt that participant, by missing something important.

If you're not needed at the meeting, probably best not to be there in the first place.

This is one of those things that's hard to measure.

Quite often I'd have to sit thru meetings that 99% of the time I'm not needed but for one specific minute I keep someone else from making an expensive time wasting mistake. It can be very difficult to determine what you're actually needed for in IT/Operations stuff.

Someone who is neither contributing nor necessary to a meeting may still be required to attend the meeting. For example, a mandatory training meeting includes people who are being trained, who are in this category.

If the meeting fails to accomplish its objectives in 50 minutes, then participants may excuse themselves with a clear conscience, but they may find themselves less-informed than coworkers who chose to stay for the entire session. Especially if there is "Q&A" for clarifications at the end of it.