How many times per hour shall I run freshclam?
You can check for database update as often as 4 times per hour provided that you have the following options in freshclam.conf:

DNSDatabaseInfo current.cvd.clamav.net

DatabaseMirror db.XY.clamav.net

DatabaseMirror database.clamav.net

Replace XY with your country code. If you don’t have that option, then you must stick with 1 check per hour.