Well, based on what I have read and common sense it's balancing act. Lower temps decrease it's effectiveness. On the other hand leaving your juices out at 'room temps' risks spoilage to bacteria not just yeast fermenting the juices. 36 hours seems like a LONG time to leave juice unprotected without the addition of K-meta/Campden tablet(s)
And of course it is recommended to add pectic enzyme or pectinase well before you add k-meta as it also inhibits pectinase/pectic enzyme function.
Personally I would go no longer than 24 hours without introducing K-meta to the juice. Even if it inhibits the function of Pectinase, there is no indication that it totally prevents the function. So I would go with a 24 hour time limit and then add K-meta and then 24 hours later check SG and pH and once adjusted pitch the yeast.