Depending on what you sells, you will notice some general selling patterns during different time of the year.
For most Ebay Powersellers, September-December are the best selling months, due to Christmas.
For new powersellers who start their business in these months it sometimes comes as a great shock to them that their sells during the summer (June/July/August) slow down.
Many powersellers use this time for research and to find new markets and products.
Of course some people will find the summer months are their best months e.g. if you sell swimsuits or summer clothes, and staple goods like stationary are more likely to sell through out the year.
So please be warned specially in your first year of trading, sales might not stay this good, or might even get better depending on when you start.
Due to all of the above, you might find during the summer is the time to sell more in your ebay shop and a little less in your auctions.
Ebay fees can ad up.