It's nice to clean up the site, but be careful of the side effects. Every time you edit a question or modify its tags, it gets pushed to the top of the recently modified list. This means editing 20 questions in a row, especially old ones, is a bad idea. Someone did this recently and now we have nothing but old junk on the first page.
A little cleanliness is good, but a lot makes a mess. I'd say not to "fix" more then 5 old questions at a time until those are no longer in the recent 50 active questions, then you can do it again. Everything in moderation.