Could it be related with your database? How often do you update statistics on the DB?

I can't link to the Tridion 2009 documentation - because it's offline only - but the process for 2013 and Oracle is [documented here][1] and for SQL Server you should just make sure you run `exec updatestats` regularly. I think it didn't change that much from 2009 times.


  [1]: http://sdllivecontent.sdl.com/LiveContent/content/en-US/SDL_Tridion_2013/idheading-158521840