Some questions get closed because they are perceived as time sensitive (including 1-2 of mine). I see other questions that are open which I, then, consider as time sensitive like those hard drive recommendation questions. If you think about it, there are lots of discussed tools, software, process service.. etc which over time become obsolete or irrelevant. But never mind that.
If these type of questions are a big issue at the Q&A sites, why not have an expiration option, set by the user, where after that date, the question self deletes? So my $400 CPU question will be out of date next week, let it expire next week then.
I see the problem with search engines. They will have links to deleted questions.
Or a status indicating the topic is considered old or a voting system to expire questions over time?