Conventional advice is to add another box when the bees have drawn and filled comb on 70-80% of the bars in the current box.
> On my screen, at the top, far right of the Thread (above my comments) it shows that I'm in Fairbanks Alaska (zone 1).
I see that now too. From what I recall, when I wrote my comment above your location was simply shown as "United States", but perhaps I was mistaken.
ultracrepidarian >> noting or pertaining to a person who criticizes, judges, or gives advice outside of his expertise