Pi-hole checks for updates to the ad lists it uses once a week, via a
cron job as shown below.
# Pi-hole: Update the ad sources once a week on Sunday at 01:59 # Download any updates from the adlists 59 1 * * 7 root PATH="$PATH:/usr/local/bin/" pihole updateGravity
Please note that the Pi-hole software will not update itself; this just checks for updates to the ad source lists. We leave any software updates to you do of your own volition.
It's not really necessary to check more often then that, and in some cases can be detrimental to you and/or the maintainer of the list. Many of the list maintainers institute a rate limit and if you exceed it, you won't be able to download more updates from them. In addition, we suggest you respect the bandwidth of the list maintainers by not excessively downloading the lists.
For both of these reasons, Pi-hole will only download the lists if there is a difference between the locally cached version and the remotely hosted one.