What you really want to learn as a result of this question is whether the candidate was around for the end of the project. Does the candidate have the stamina needed to see a project through to completion, or does he lose direction near a project's end?
If the candidate gives a vague generalization of how the project ended or openly admits that he was not around at the project’s completion, you should see this as a warning sign. It is up to you to determine whether this occurred once or a number of times. You might accomplish this by asking about other completed projects or by thoroughly checking his references. If he does admit to not seeing a project through to the end, it is in your best interest to find out why.
The right answer to such a question would involve a plausible story explaining the completion of a project, regardless of its time frame. If the candidate was involved through the completion of the project, you will be able to tell by the details he provides regarding the project’s final stages, its implementation, and the overall reaction of his team members.