I pondered hard on this one. I didn't think it'd be a good idea to hold the sale in spring because that clashes with the big Glebe sale. Fall seemed a reasonable alternative - weather still good and people are pumped from their holidays. Labor Day weekend came to mind but I thought hmmm, some folks might still be away on vacation. Also, this is prime moving time for students, coming from out of town. Moving vans and garage sales don't mix well.
So after bouncing the idea off friends, I chose the first Saturday after Labor Day weekend.