Don't panic! The timer should just be when you can trade the item to another player or put it up for sale on the GTN. It won't disappear or anything.
what he said. the item won't disappear unless you delete it somehow. the timer is just if you wanted to sell/trade the item.
if the item was a piece of equipment and you wanted to trade it after the timer expired, you have to make sure not to wear it, as that will cause it to bind to you even before the timer expires.