Thanks for your responses, even if they were about 6 months late (lol). The reality I came to (and based on GulfCoastInspector's post, still am in agreement with) is that API/NBIC simply does not define what is considered the opposite of "In-Service". I would think that if you are publishing codes, recommended practices and guidelines for the inspection, repair and rerating of "In-Service" vessels and piping, naturally you might throw in a disclaimer of what condition would exempt the vessel or piping from being considered "In-Service", as that is going to be an obvious question or attempted loop-hole of many owner-users, right off the bat. However, the only real committed answer or lack thereof to this subject must be made by interpreting your local jurisdictional verbiage and cross-checking it against the owner/users documented practices, if they are documented at all.
I don't understand why this is an un-touched issue, with regard to API. I wonder if at some point they will recognize this as being a potentially abused loop-hole, due to lack of definition, and maybe offer additional recommendations/guidance/clarification as to what can reasonably be considered In/Out Of Service, at some point. Until there is a RAGAGEP in place defining a thing, that thing will continue to be misunderstood by some, perhaps understood and acted upon by others, but not consistently applied across the industry, due to the lack of guidance or lack of any generally accepted practice for all to follow.