As Mike said, the ending time of Sunday evening is when most G scale listings seem to end. That's when I schedule most of my listings to end. The duration of the listing is another issue however. Seven days is the most popular, it seems. But the thought arises that a short listing time might get someone's attention, in that they would want to act on it before it goes away. On the other hand, a lengthy listing might allow complacency. Buyers figuring that the item will be there after they have viewed all other listings in their category. By that time, the buyer may have expended his funds.
What Stephen pointed out about March and April may explain why my sales are limp at the moment. In this case, a long listing time would be beneficial.
I suspect that the discussion we are having is why marketers have a job.