The annual event was our best work. Making it monthly nearly ended it, and the reasons had nothing to do with demand.
The audience does not scale linearly
The same people will not attend twelve times a year. Monthly means either a much larger pool or a rotating one, and we had planned for neither. Attendance held for three months and then fell by a third.
What broke first
Not marketing. Operations. Every event had been run on personal memory, and personal memory does not survive twelve repetitions. We were rebuilding the same run of show from scratch every month and making new mistakes each time.
What fixed it
A template: run of show, vendor list, checklist, and a post-event review with three fixed questions. Once the event was a process rather than a performance, frequency stopped being the problem.
Pricing had to change
A yearly event can command an occasion price. A monthly one cannot. We moved to a lower ticket price with a membership option, which turned out to be more predictable revenue than the old model ever was.
What we would tell someone considering it
Run the same event twice in a quarter before you commit to twelve. The second one tells you almost everything the twelfth would, at a fraction of the cost.