There are no rules about this from the perspective of MA World Services. Unless the group conscience of the group/meeting says otherwise, members are free to vote at any and all meetings that they attend.
The goal of MA World Services is to represent every member’s voice within the fellowship. It is understandable that members may want to vote at all the meetings they usually attend, if they have multiple “home groups,” groups/meetings within the same district, or groups/meetings with multiple occurrences per week.
When the annual Conference motions are presented for groups/meetings to vote, nothing prohibits members from voting at more than one meeting as far as MA World Services is concerned, and in many districts, members do traditionally vote at every meeting they attend.
Autonomous meetings are free to decide whether or not there are any such requirements for the group/meeting, including how to obtain a group conscience for the fellowship-wide vote on the proposed changes. Some groups/meetings may uphold a group conscience regarding if a member has already voted at another meeting. While other times a member themselves may personally carry a belief about how many times they would like to vote, even though there is no group-wide requirement in place limiting the number of times they can vote.
“Every group has the right of self-government undertaken without outside control. Every group can manage itself exactly as it pleases . . [and] may make any decisions or adopt any format it likes.” -Tradition Four, Life with Hope 3rd edition. pg 71-72
MA World Services does not have limitations regarding a member’s participation in one or more group conscience business meetings.