15 (goal) minutes with a 10 person team.

Everybody didn't zone out every day, but most did, most of the time.

It's also detrimental to morale when you realize that other people are zoned out through standup. Nothing much more frustrating than when a coworker asks a question that was answered in the "meeting" we were all just in.

Frankly, it's a huge opportunity for the listeners to shine. (Yay for being a listener)

Exactly. It's a waste of time. Best to give a direct message or face-to-face telling the person what they need to know. Or not say anything if nothing is needed. At most, I'd say weekly meetings that were a mix of tracking project status and fun just for team-building purposes. Keeping people connected.

I'm a project manager/scrum master, with a team that varies from 6 to 12 (roughly half the team is semi-permanently on-loan to other related projects/teams).

My daily stand-up is usually 5-10 minutes. About 5 minutes of the standard "what I did, what I plan to do, and what's in my way". And 0-5 minutes of resolving problems (figuring out if I need to escalate, or if another team needs to be involved, etc). Anything longer than that, and we schedule follow-up meetings with a more correct set of attendees.

I've found this with big and small teams. With small teams you already know what everyone is up to and with larger ones the meetings go on for longer.