Once a question has been adequately answered in the judgement of the OP. I'm not saying we should definitely do it though. It only really works if everyone does it and its of limited value, but does come in handy on occasion. Anyone else have an opinion?
It's got some value if the question is very specific and has a simple solution, like a software configuration question for example. The problem is that most questions aren't that specific and are fairly open ended, meaning that there are many possible solutions for the same question, so closing the thread or marking it solved just because a single person posted an answer wouldn't make any sense.