There are multiple approaches, but I preffer this one:
in EPP set custom attribute on the node with timestamp of the last log event (either via script action, or directly in rule's filter script), then add scheduled task with the script, which iterates over nodes and check if time in custom attribute is older than a threshold. If it's too old - use PostEvent to inject another event in to the system.
in EPP set custom attribute on the node with timestamp of the last log event (either via script action, or directly in rule's filter script), then add scheduled task with the script, which iterates over nodes and check if time in custom attribute is older than a threshold. If it's too old - use PostEvent to inject another event in to the system.