Is that why it usually tells you that you can't find any trading partners after a little bit? So that you don't overflow the cache with, whatsay, one species of breedject?
I do it when I feel like it and have gotten a ton of cool breedjects, and I usually wondertrade my own breedjects. I usually do this as soon as I think that different people are on and I think about it, but if I had to put a time to it, probably around 10 pm EDT and at around 6 am EDT. Sure, you get a lot of chaff, but when I do I just go ahead and release it so it isn't circulating around the WT pool endlessly.