Changing webinar levels from 1000 to 3000 during event

Just checking:  Will any of your webinars be concurrent (2 or more at the same time)?  I'm assuming they will not be concurrent, since you mention you have "a license", not multiple licenses.

The Webinar Join URL (with the embedded Meeting ID) for both Meetings and Webinars doesn't change once the session is created.  The capacity information assigned to the host is checked as attendees are joining the in-progress webinar.

It's my understanding that an increased capacity can even be enabled while the Webinar is in progress.

About 2 years ago I was attending a 3-day training event for an organization I belong to, using Zoom.  There were over 800 registrants, and there were concurrent education sessions, each likely to have under 500 attendees.  But there was one special session, and apparently the meeting hosts were assuming that 500 or or less would attend... and had planned to Live Stream to YouTube if the attendance reached 500+.  Unfortunately, when the attendee count reached 500, the hosting company had problems establishing the Live Stream, and (my understanding - I was just an attendee at this event!) they increased the capacity of one of their webinar licenses to the next increment... and we watched as the attendee count reached just over 800.