"Closure" is used as a missiological term with eschatological underpinnings. Most people who talk about "closure," however, aren't using it in that sense. When we use the term missiologically with people who aren't familiar with this technical definition, we have to remember it carries a lot of implied cultural and emotional meanings.
When people speak of "closure," they might mean:
To seek "closure" in anything (even missions), for any given individual, might be colored more by these emotional meanings than by any textbook missionary definition of the phrase.
If "finishing the task" or "closure" carries with it these meanings--how might that affect the strategy we use?