The size limit is imposed by the Database backend. For example if you are using SQL Express prior to 2008 R2 the limit is 4GB. SQL Express 2008 R2 has a 10GB limit. Full SQL basically has no limitation.
It is recommend you enable some type of database maintenance in the EndPointSecurity console to backup events or delete events older than a specified period of time.
This can be done in Configuration > Database backend > Database Maintenance.