Hi Norman,
Unless you are using completely out of the box configurations of Windchill, I would consider life cycle states as merely labels that you as an administrator can determine the functionality of.
Release is a little unusual by default. There is a preference that designates a state as one where when WTParts enter it, an XML file is reduced. If you change this preference, "Released" is generally no more "special" than say "Production" - though this assumes you are not using the out of the box access permissions and a few other configurations.
You can set access control rules by state, one of which is where a user can view the object. This will determine whether they can see the object's information page, it does not determine whether it appears in the Structure. However, you can create table views for the Structure table you refer to that will filter out obsolete objects. Personally, I would not recommend that. To me obsolete objects must be removed from all the BOM they are in before they are made obsolete, but that is a business decision.
Regards,
Toby
