Hi, depends a lot on your toys but the closer to Christmas the shorter the listings duration need to be to catch the inevitable last minute buyers.
Then PayPal option for rapid payment and some Buy it Nows and fast delivery are essential especially with postal traffic rising and swamping and slowing the postal service.
My feeling from past experience is from mid November onwards as by then the decorations are well into the shops and small and big kiddies start dropping less than subtle hints.
Look around at the high street stores for guidance in your vicinity and by all means start writing your listings now so you can upload them nearer the time. Scheduling is free on Auctiva so use it to your advantage, write now post later when other eBayers Christmas selling starts. Watch similar eBay sellers closely particularly their closed listings to see what sells, what does not and for how much.
I would also avoid posting delicate toys into the Christmas postal crush can cause too many tears at a crucial time.
You will probably be lucky to get much response to this from competitors, I'm not so I'm answering