Just realized, from my experience upgrading WriteLit.com, that you can speed up your Drupal site by regularly emptying the following tables.

1. accesslog
2. cache
3. sessions
4. watchdog

It may also be a good idea to stop using the Search Module because it has bugs anyway, and it might be regularly consuming resources because of the indexing that it does. What I mean by bugs is that I've learned during the upgrade that there might be redundant entries during indexing, and this produces errors once you try, for example, to restore the database.

Besides, Google search does a better job of indexing the site. And you also get additional earnings from clicks from Google search ads. :)