When you say 'update' do you mean rebuild or reorganize or is there a fragmentation level that your maintenance plan uses to decide whether to rebuild or reorganize.

If you are using the built in maintenance stuff, I would recommend the Ola Hallingren indexoptimise script as it will rebuild or reorganize or do nothing depending on logical fragmentation levels.

Could be you are explicitly rebuilding everything but you really only need a reorganize and an occasional index rebuild since it is running daily.

http://ola.hallengren.com/sql-server-index-and-statistics-maintenance.html