Does anyone know of a situation in which a terminal disclaimer would not be appropriate in a nonstatutory double patenting rejection where the asserted patent and pending application are co-owned?
The PTO has used terminal disclaimers for a long time when a single entity is trying to obtain several patents that are very similar to one another. The terminal disclaimer typically links the term of a pending application to the term of another patent. Thus, the impact is that the patent term will be shortened.
The usual patent term is 20 years from the filing date. With a terminal disclaimer, that term might be cut short to say 18 years. So, what we are talking about here is the last few years of the patent term.
Companies that care about those last few years (such as pharmaceuticals) typically try to refuse to submit a terminal disclaimer. Many others go ahead and submit terminal disclaimers because it makes the patenting process easier.
In most terminal-disclaimer situations today, the pending application has the same priority filing date as the related issued patent. In that situation the two patents will have the same patent term anyway (because patent term is calculated from the priority filing date*). However, even in this situation a terminal disclaimer could be harmful because it could cut eliminate any patent term adjustment due to USPTO delays in the prosecution.