Instead of installing them 1 by 1, you could extract each one into the "templates" folder, then in the Joomla Backend, go to:
Extensions >> Extension Manager >> Discover
Then clock the "Discover" button in the top right, whch will then display all your extracted templates that haven't been installed properly. Select them all and click "Install".
This will make life a little easier and be quicker I would have thought.
As Valentin Despa also said, Joomla 3.0 is the short term release, therefore if you want a site as big as something that requires 250 templates, I would recommend using Joomla 2.5, as it's the long term release and more stable.