Sitepoint doesn't seem to have performed very well for me with services. I listed a website for sale there & it resulted in a successful transaction. I'm tempted to say "best times" similar to those for ebay.
All of my stuff that wasn't that great went so fast over the chrsitmas period however now I have some great bargains up for sale and am recieving no interest at all. Tonight if you look through the listings, theres not one thing sold.
I dont know why but christmas seems to be the luckiest time.
I would comment that those in the business under the age of... 22 will typically do more e-work in the summertime, so maybe thats a good time?, tho your more likely to get that cheaper, younger crowd then...