We do everything we can to keep our monthly general membership meetings to an hour or less. We hear reports from Board members, Committee Chairs, staff liaison, & the principal, and address any old or new business that's on the table. Most of the actual work of the PTO occurs between general meetings, with most decisions made online.
We do have our Board meetings in the hour before the general meetings, and much more actual work occurs during that hour.
It's sometimes hard to keep the meetings short, and many members often stay after the meeting ends to continue discussions and brainstorming sessions.
Our monthly general membership meetings run about 1.5-2 hours long. We conduct business (i.e. bylaws, standing rules, membership approval of budget, acceptance of minutes & treasurer's reports), hear committee reports and general plans of work, hear the teacher's representative report/feedback/requests, update the membership on various things in progress (agreements with sister PTAs, etc.), and so on.
The majority of the detail planning of events, etc. takes place in separate committee meetings (or email, telephone, whatever). We will brainstorm ideas if a question comes up, or occasionally a committee will ask for the membership's guidance on something.
While you are waiting to hear from other parent group leaders about how they structure their meetings, here are a few articles that I think you will find helpful:
What is the structure of your monthly PTA meetings? Do you use your monthly PTA meeting to plan events/activities (volunteers, logistics, etc) or do you use it to cover current business? Or both? What timeframe do you keep it to?