I add it and most other sugars at high Krause or just past that. I figure that the yeast are well on their way to metabolizing the main meal and give them some dessert. Seriously, I think the complex sugars get a full working over, so by high krausen, I'm less likely to cause a stall in the fermentation rate if introduced earlier. It could be overkill or unproven but FWIW it's what I do.