You could list a few days into the New Year, enough time for people to recover from any NY celebrations they will have had, and enough time for new years resolutions (to buy new sites from SP?!)
Or as you said wait until Spring time, when people will have got over the expense of Christmas.
What is it you are planning to list? A domain? a site? or an e-commerce site - judging by the forum area this thread is in
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