My lodge holds LEC/LEB meetings at least 4x a year. Typically, they are about 1 month prior to a major lodge activity. Attendance by the youth seems to depend on a couple of simple issues: advance notice, a phone call to remind them, and a meeting that actually serves a purpose (to plan).
Many times in the OA people believe that since something is on the published calendar that the officers, chairmen, and advisers will attend. The vast majority of these people typically have other Scouting responsibilities and a simple email or phone call to remind them will help increase attendance.