Drop traffic at certain time

I want to limit internet connectivity at certain time for vlan. I added rule to drop traffic at traffic rules page in LUCI. However, already established connections continued to work.
In order to bypass forward rule for established connections I added following custom rule.

chain user_pre_forward {
        type filter hook forward priority filter - 1; policy accept;
        iifname "br-lan.2" meta hour != "09:00"-"22:00" drop

Now, if flow offloading is disabled everything works intended. However, if flow offloading is active established connections still flow.

It looks like offload tables should be purged at time boundaries. How do I do so?

Would service firewall restart not be sufficient?