Almost always once a day, currently between 9:00 and 9:30 am GMT. I scanned back and the last time there was a twice a day was 23 Dec 2021 and very few no update days.

-Al-

On May 25, 2022, at 9:13 AM, G.W. Haywood via clamav-users <clamav-users@lists.clamav.net> wrote:

Since it's just using DNS requests to check for updates it's very
lightweight.  I feel sure you can make the queries as often as you
think is reasonable, but do bear in mind that updates to the official
signature database aren't especially frequent - a couple of times a
day or thereabouts at most I think.