Does your group meet monthly? Quarterly? Have you discussed what the right amount of meetings to have is? You don’t want each meeting to be too long. Actually, we have two questions here,
1. How long do you want your meetings to be?
2. Would you be willing to meet more frequently to have each meeting be shorter?
Each group will find the balance that works for them. Maybe it is a problem getting the board together, so if you do meet, you want to make it worth your while.
Some groups meet quarterly but have day long meetings. The board members who complain about the meetings being too long, might need to consider how to fix that. Maybe more frequent/shorter meetings is the answer. Maybe there is too much off topic discussion?
If you are finding that your board meetings are long, then perhaps delegating more to committees could be the answer, rather than having that discussion at the board meetings. There is an ideal length for board meetings, your group should experiment until it finds it.