I know it's been mentioned a few times but can't find it: after how many days will a vote to close fade away if the question does not accumulate the five total votes needed for closure?
I'm pretty sure the Privileges page has a typo for this value. There certainly are close votes here on Meta older than 2 days, so if this has been changed, it's very recent. The "old" expiry threshold was 4 days.
I've test voted-to-close this question. We'll see how long the vote hangs around.
EDIT: It's now been 2 days and the test vote is still around, so I'm assuming the threshold is still 4 days and there's a typo on that page.
Jeff recently said here (10k only), "Once those [close] votes expire or reach the threshold (2-4 days) this will never happen again" but what I think he meant was "Once those [close] votes expire or reach the threshold (in 2-4 days) this will never happen again."
Jeff was actually the one who added that Privileges text in revision 5 of the wiki post. Which means this isn't tied to any system setting, and therefore is most likely a typo. Or, some sites do have a 2-day threshold, just not on Meta, and revision 5 was a copy/paste job where the threshold value wasn't modified. In that case, the answer to this question is: it depends on the site, but most likely 4 days.
EDIT: The vote has now decayed away. I wasn't checking when exactly it disappeared, but it's somewhere between 4 and 5 days. I have updated the Privileges wiki on Meta to say 4 days. This has been the default for as long as I can remember, so if there actually is a site (beta sites?) where the threshold is different, a mod can modify the wiki on a per-site basis.
Timestamp of the comment on the question that I erased: Oct 14 at 17:34 -- I test-voted just prior to posting that.
From the privileges page :