Huge database size



We are running piwik 2.1.0, tracking 5 sites totaling about 5.000 visits per month and one site with about 850.000 visits per month.
We started analyzing the 5 smaller sites in November 2013 and the large one in April 2014. The Piwik database grew to more than 200GB to this date. Visitor logs and reports were not purged yet and we are trying to figure out a reasonable purge policy.

Is the database size of 200GB+ is something to normal for this kind of site?
What exactly do we lose if we delete weekly/daily reports? While testing the DB purge nothing apart from Transitions seems to be missing.
Edit: Can I set different purge policies for different sites?