At the client I work for we have 2-3 meetings every other week that are frequently attended by 50-100 people. One is a "demo meeting", where teams present their

At the client I work for we have 2-3 meetings every other week that are frequently attended by 50-100 people. One is a "demo meeting", where teams present their work, the other one is called "architecture guild", where people discuss the system's architecture, how to improve it, recent changes and developments etc. Attending the meetings is not strictly mandatory, though. All-hands happen, as you say, approximately every 2-3 months.