Can you change the frequency of the configuration backups to something other than 8 hours for schedule 1? daily for schedule 2 and weekly for schedule 3. Perhaps daily for schedule 1, weekly for 2 and lastly monthly for schedule 3?
The only option available to reduce the number of backups: http://docs.netapp.com/ontap-9/index.jsp?topic=%2Fcom.netapp.doc.dot-cm-cmpr-920%2Fsystem__configuration__backup__settings__modify.html
You can probably keep just 1 8-hour, 1 daily and 2 weekly.