Question: How about we create a new status, **Archived**.

A moderator could **Archive** a question. This would allow rep from the question to still be counted, and a special search '**isarchived**' could be used to find it, but it wouldn't come up in normal searches, and would be marked so that Google wouldn't use them for search results.

This way old questions that aren't currently relevant, but were good for their time and have historical interest and maybe good discussion could be looked at by those who are interested, but those who just want to search for current stuff won't be bothered by them.

**Note:** This is for Meta sites only, and *maybe* for those huge subjective monster questions on SO.

Answer: 
I completely agree with @devinb that this shouldn't apply to Stack Overflow. However, based on your latest edit, I think that having such a feature for meta-sites may, in fact, be a good idea.

The Gmail archiving model can be applied here, such as for old bugs and feature-requests that are [status-completed]. There should be a viewing mode that hides them from search on request.

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**UPDATE:**

Some people have suggested simply locking and closing (or even deleting) old posts. This isn't the way to go. Instead, we should have a viewing filter, where old bugs and feature-requests that were completed are hidden (at will). People can still contribute to those posts if they see fit - locking/closing wouldn't allow that.

On another note, I'm all for closing/locking massive "poll" posts.
I believe it should apply to Stack Overflow. Just because a question is no longer valid, does it mean that people who put time into it should lose reputation points because it's deleted?

There are two different issues here: 1) The content 2) the time and effort put in by people, which is rewarded with reputation.

Just because a question is no longer valid, does not mean that the time and effort put into it becomes invalid as well.

I don't think this applies for poll style questions. That's a different matter in that they are not, in fact, much effort.