| My question is do they judge the size of it before they go in? Has anyone else had this problem?
Yes they do size it up! Sometimes they actually reject based on this information. In this case however no. The item would have to be many times bigger than that to just reject if it was hungry.
For example, at the CARA conference yesterday one of the presenters produced a photo of an imbricata of 4kg in size consuming a 4kg tamar wallaby. Whilst it would probably not eat again for 6 months it shows you they are adapted to take enormous prey if they have to.
In your case it probably has to do more with the husbandry. During the cooler months antaresia and many other snakes go off their food not only in relation to the fall in temperature, but in response to photoperiod. Your python looks big and healthy and may not eat again until Spring, which is fine.
What are you cage temperatures like, ambient temp and hot spot temp etc.
The only issue i'd mention regarding live feeding is that you never leave the rodent unattended for the snake to restrain. If the snake doesn't want to eat, many rodents can get savage and attack the snake.
Although everyone knows it's illegal many people do it to entice a feeding response. If you do want to wean, often feeding a fresh killed straight after the live works well, until eventually they accept fresh killed. Or if defrosting, try defrosting dry in a snap lock bag so the mouse is dry when being fed (sometimes that works).
As i said i suspect here that the snake is just cycling itself for winter.
Cheers | 
