Items that are automatically relisted should remain on your watch list or other lists.
But items that are purchased or go out of stock and are not restocked -- or items that end and are not automatically relisted -- will disappear from your list after about sixty days. In some cases you may see a link on your list ("see relisted item") for items that have been manually relisted; in that case you must follow that link and add the new item to your list before the old item expires and is removed from the site (and your list).
Keeping a list current requires periodic maintenance. Once items are removed from the site there is no way to add them to your list again other than searching for similar current items and adding those to the list.
