In my experience, the skull and bones will disappear in one of two ways:

1) If you retrieve all of the items on your corpse, the map marker will despawn within a day or so; or

2) If you die again, your new corpse will spawn a new skill and bones at its location on the map and the older one will despawn from the map immediately. Your old corpse and its possessions will remain. You will see it if you get within visual range. The map marker, however, will despawn.