I've been taking a lot of care to keep my categories manageable. Too many, and it gets hard to find the one you're looking for - although using a tree helps. Too few is just as bad, though.

It's time to add a national park category to my blog. I've been to more than 20 of them; have photos from Yellowstone, Glacier, Yosemite, Zion, Arches, Canyonlands, Mesa Verde, Mt Ranier, North Cascades, and Olympic National Park, recently enough that I don't have any photos online yet. Three of these are in my home state, and finding their way into my blog posts. Enough that I should add a link to my sidebar for the tourists.

When other people get to this point, do you go back through your old posts and apply the new category to them? Or just from that point on? Is there an easier way than editing the post? That's pretty tedious when you use Google Maps...

I'd probably just apply the new category to the old posts as well, as long as they don't disrupt your permalink structure.

Also, where exactly were you planning to add the new category, at the top?

I used to include a post in every category possible, but now I only use one category per post. I think all the categories creates to much potential duplicate content issues. No proof of that. I saw the advice somewhere and it made sense to me.

Thinking of it as an end user if I decide to go through a blog and read it's old content I might click on a category and start reading. I think I might get annoyed if the next category I clicked on presented mostly the same content.

I think it's up to you if you want to go back and change categories or add old posts to the new category. I'm not sure how important it is.

Good question, James ... and I'm not exactly sure where it would go. Probably under travel - one of the reasons I decided to go through Southern Utah on a particular road trip instead of AZ was that the state has five national parks.

That's an interesting point ... I thought long and hard about getting rid of my archives section all together, and finally decided against it because I figure if a person wants to go back and read older posts sequentially, that's the best way to do it. I've been assuming people would use the categories to read back in a more narrow way.

So as I create new posts, I tend to mark them with the categories that seem appropriate. With the tree, you get this wonderful functionality so that if a person clicks Travel, they get posts I make about the Rockies, because it's a child node. So I tend to go down to the most specific category that applies, although a lot of posts are about travel in a more general sense; the allure of the open road instead of, say, US 395.