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it depends on the editor and category. i have one listed on the same day! another the next day. and the last one still isn't listed yet.
the one that isn't listed yet is in a category without an editor. now i'm waiting for about 4 weeks to get listed.
Editors have access to all the lower categories of the categories they are listed in. That is, an editor listed in some category like Business/Widgets/ can edit throughout Business/Widgets/Fuschia or Business/Widgets/Spinning/Clockwise . And editors are generally encouraged not to list themselves in subcategories where they can already edit, so as not to scare off potential new applicants.
So, if the "last updated" message indicates that a category that appears to have no editor is in fact changed on a weekly basis, you may surmise that someone higher up is taking care of submissions. On the other hand, if you've had a submission waiting but the category hasn't been touched in three months, you may want to send feedback to one of the editors in the parent categories asking them to have a look.
Simple answer: depends a LOT on where you are submitting to, and how conscientious the editors are. The commercial cats are being so heavily spammed that this is definitely causing problems. The spam problem is so intense that the spammers are spamming even non-commercial cats hoping an incompetent editor adds them by mistake. I know, I recently became the editor of a PR7 branch under Recreation: and most of the work was cleaning up the spam. :( Dealing with the unrevieweds laying around was the easy part. As someone stated editors can edit in any cat below them. Thus, there aren't really any cats with no editors. While theoretically several other editors are below me, as only 1 has even logged in within the last 2 months I decided to deal with all the unrevieweds in those cats. However, while my cat space goes high up the tree, it only has several hundred sites listed in total. It may do you little good that there are editors of higher cats then yours around if they control cat space with tens of thousands of sites listed, and a huge number of unrevieweds.