A good friend and my former manager wrote:
My all-time record for back-to-back virtual meetings in one day is 16. What’s yours?
Food for thought: We would never do this to ourselves in an office. Why do we think it is okay when working remote?
I started writing a comment and LinkedIn, in its passive-aggressive wisdom, lost my draft. So here’s a longer response on my own platform. 
First I don’t think 16 back-to-back meetings is ok. Even if this is 16 half-hour meetings, that’s exhausting and likely counterproductive by around meeting #4. I used to work with a mentor who would teach me SQL for hours at a time. He’d regularly ask if my sponge was full. We all have a natural mental capacity that can not be exceeded[1] so he didn’t want to spill knowledge that I wasn’t soaking up. I usually hit that limit around 2 hours, but a half hour break would often be enough to let me start a new session.
For many people, virtual meetings are less stressful than in-person meetings because you can let your mind wander without people necessarily noticing.[2] A lack of non-verbal social cues, in turn, requires more work from people hoping to engage with each other. So on top of the substance of a meeting hitting our mental cap, we’re more likely to hit our social-interaction cap too. Virtual meetings make it easier to tune out when needed (so longer meetings are possible), but there’s no getting around the limits of engagement.
When I worked in an office, I never had scheduled 1-on-1 meetings with my manager. Usually we’d talk when he stuck his head in my cubicle a few minutes after I’d arrived in the office.
Going remote meant managers intentionally scheduled regular calls to check in. Year-end performance reviews stopped being a surprise since we’d been talking about how I was doing all year long. No reason we couldn’t have had those in the office, of course. Being remote left no question that those meeting are necessary. Managers can no longer pretend that daily 5 minute chats are a suitable substitute.
Of course that’s not ideal for managers of large teams. At one point I had 4 direct reports at College Confidential. That was quite manageable. One team meeting and 4 1-on-1 meetings isn’t so bad. But as a team gets larger, managing gets harder. As Frederick P. Brooks, Jr. wrote:
If there are
nworkers on a project, there are(n^2-n)/2interfaces across which there may be communication, and there are potentially almost2^nteams within which coordination must occur. The purpose of organization is to reduce the amount of communication and coordination necessary; hence organization is a radical attack on the communication problems treated above.—The Mythical Man-Month, “Why Did The Tower of Babel Fail?”
Notice this problem predates remote work. The solution Brooks recommends is division of labor and specialization of function. Remote work allows people to put in longer hours and removes some of the barriers to back-to-back meetings.[3] But it doesn’t fix the fundamental limitation of human communication.
Now there are times when many meetings is necessary. Performance-review season, for instance. Still, if people in your organization regularly lose project management Tetris, it might be time to strengthen the organization. Split off roles that would benefit from specialization and consolidate work so that lines of communication can be shortened. Letting people burn out in meetings isn’t doing anyone favors.
See also: Give yourself built-in margin