I have almost given up second guessing ebay!
Times that I have thought would be slow haven't been, and vice versa.
As it is worlwide, there are so many variables. In the UK Novemeber is quite good for buying because of your thanksgiving holiday and you all seem to be off ebay! Summer can be quiet, but then I have also made some of my best sales in July.
I don't sell at all in December, but that is so I can concentrate on Christmas etc and have a bit of a break, I sell from the 1st Jan through to the 30th November, occassionaly taking a week off, but that is more to do with family and fairs etc than with ebay. I list on a Saturday as that is convienient for me, but have been known to list on a thursday if ebay are doing a special offer.
I list whenever and keep my fingers crossed!
I have a crystal ball too - but I think it must be broken!
Sara