at core/ArchiveProcessing/Period.php line 82, I’ve changed this:
if($name == 'nb_uniq_visitors') continue;
to this:
if($this->period->getLabel() == 'week' and $name == 'nb_uniq_visitors' ) continue;
it will mess with user reports for a while, but it is the best I can do for now.
the future plan is to create a user table by month, that looks like will be far smaller than log_visit