J.D.
I think it depends on why you are having the garage sale and what you are selling. I had one in May because I was moving. I didn't want to haul off a bunch of stuff I needed to get rid, so I was motivated to sell. Anything I made on it was worth it to me. I got rid of a lot. Made about $250. I advertised the sale on Craig's List a couple of days prior.
I only committed to one day. Anything more would have been a waste of my time. But not having to haul off the extra large items was a big plus for me when moving out.
If you have large or more valuable items to sell and want to make money, you might do better posting the individual item on Craig's list.