conduct is determined by auction on eBay or determined by the seller? and usually how long the auction time?
what do you mean? You can choose how long you want your auction time - 3 days 5 days or even more than a week. Its your call.
Auction is done by seller. It depends on seller how long he/she want to keep the product for auction. Seller selects number of days for auction.
You can also cycle the auction periods. As a long time member I've seen auctions that go on indefinitely when someone has a large supply of an item.